Why did the Korean War result in a stalemate?

Chinese were much better prepared for war then North Koreans

War stared in late June 1950, but Chinese intervened only in late October when North Korean demise seemed inevitable. In a period before that, main opponent of US and their allies was North Korean army (Korean People's Army - KPA ) . Now KPA was mostly Soviet creation after WW2 (from 1948 onward) . It did exist as guerilla army before that, but it was not that numerous. Soviets wanted quickly to create conventional army for communist regime, and in few years their created "pale copy" of their own armed forces. The reason KPA was just a pale copy of Soviet Red Army is simple : KPA got surplus Soviet equipment including T-34/85 tanks, Il-10 attack planes, Yak-9 fighters etc ... Therefore, KPA did look like one of Soviet armies from late WW2 period, but neither had combat and operational experience nor industrial base to support, maintain and replace losses in such mechanized force. North Korean military tried to adopt and implement Soviet military doctrine, but when US intervened in earnest they found themselves outgunned and could not much firepower with firepower (like presumably Soviets would do) . Therefore they crumbled. It is worth mentioning that US repeated "pale copy" mistake some years latter in Vietnam, when they tried to organize ARVN in their own image, but again without industrial base and proper training.

On the other Chinese army (People's Liberation Army-PLA and their intervening force in Korea People's Volunteer Army-PVA) was much more "natural" force. PLA was already huge during WW2 and from outset it was created as guerrilla army. Chinese soldiers and commanders were used to fighting were enemy had air superiority, advantage in armor and artillery and overall greater firepower. In order to counter that they employed their own tactics, using terrain, traveling by night or heavily camouflaged, using makeshift logistics (bicycle transport) , communicating with relatively primitive means like gong and flute instead of radio etc ... Of course, there was also willingness to employ large number of troops, and to sustain high casualties. Chinese were often noted as fighting to death, even using rocks when they run of ammunition like on Triangle Hill .

Overall, both China (and Soviet Union behind them) and US wanted to keep things in Korea local, without provoking WW3. There were hot headed commanders like Douglas MacArthur that wanted to escalate things to nuclear level because they could not cope with the defeat in winter of 1950, but fortunately for the world their ideas were not implemented. US joined the war in order to save South Korea, China to save North Korea. Both sides effectively achieved their goals, rest was just matter of prestige (that did cost lot of people their lives) . US also had other strategic commitments (especially in Europe vs Soviets) and they could not afford larger engagement in Korea, especially not without going again in full war mode (and general public was tired of that) . Therefore on the ground some kind of balance of power was achieved which evolved into stalemate and then ceasefire we have today.

Here's my stab at it, coming from just reading This Kind of War* by Fehrenbach.

(Apologies: my first read on the Korean War. However, the Cold War is my favorite historical period, along with asymmetric warfare).

Past the initial mad yo-yo-ing the 2 other answers have provided maps for, Truman understood that this was a sideshow . "Domino Theory" dates from 54 and he understood the Russians, and Mao, were willing to fight till their last Chinese.

MacArthur also thought it through when he literally conjured up Inchon out of thin air. It was a masterstroke, especially aimed avoiding slog-through warfare. Marines? Not happy. Navy? Not happy. With hindsight: "Wow. That's so thinking outside the box. Clever. But you can only do it once."

The Chinese, according to the above book, gladly accept the July 1951 talks, because they're again losing, most of the Chang Kai-Check soldiers Mao sent in are dead by now, and the yo-yo is now heading North, again. They've gone past Seoul 4x by now: twice heading South, twice North. They use their first negotiation month to just dig in. Heck, probably both armies were quite happy to fortify.

Later, the war has congealed into WW1, not WW2. The Chinese have plenty of artillery and tons of men to waste. Frontline is not budging and US casualties are massive. Tanks don't go up 40deg slopes. There is total US air superiority. But everything happens at night and air can only do so much with 1950s tech over forested mountains with an enemy who knows all about the death ride of the German panzers through Normandy and have no T34/85s left anyway.

The Chinese are also caught in a trap: they can defend and their infantry can overwhelm tactically, sometimes. But they won't get a war-winning breakthrough against a logistically and mechanically superior enemy. With, it must be said, very brave US soldiers: platoons at that time sometime almost die to a man, unlike in June 1950.

Later on, the fallacy of fighting with your own troops while the enemy is using their proxies' would become apparent: Vietnam for the US, Afghanistan for the USSR.

MacArthur was also right in his way. Vietnam and Afghanistan 1979+2001 show you can't beat an tenacious enemy with sanctuary neighborhoods (might be a 1930s Italian campaign that's a counterexample). But beating China straight out might have ultimately required the US to drop the bomb.

Regardless of the outcome of the Cold War, whether the US "won" or not, with its near-monopoly of nukes, nuking their way to victory in Korea would have been a horrible outcome both for all the deaths and the lasting discredit it would have brought to the US. Truman understood that.

Kennedy never did and almost got a hot WW3 from Cuban Missile Crisis (while the US had Russia-aimed ICBMs based in Italy and Turkey). Then he took the Vietnam bait.

One other thing I remember from all my Vietnam War books, but which only one book, Rise and Fall of an American Army made a point of: the US troops in Korea or Vietnam did not magically appear, at great cost in blood and money. US units in more critical areas, like the Fulda Gap, were understrength vis-a-vis their Soviet counterparts. This is not a game you want to be playing for a long time.

There's a also a strong political dimension, both domestically (the incumbent Democrats would lose the Presidency) and internationally (the UN partners were onboard for saving South Korea, not so much for extra war aims).

US should have the capability to push the Chinese

Tactically, at the Korean level? Maybe. Strategically, at the global level? No!

1953? Stalin dies and negotiations unlock long enough for the war to be cease-fired.

The US had no overriding national-survival reason to persecute the war and plenty of reasons for being content in having achieved their original aim: giving Communism a cold hard check and saving Korea.

Without too much of the really unethical crap they pulled in Latin America and Vietnam later on. And would have been an ongoing liability had the USSR not collapsed past 1985 - being really unpleasant to people wins no hearts and minds.

I suspect (that would be a different book) that the Communists had alienated the South Korean civilians enough during their occupation that their population would not need much reminder (beyond a SK military dictatorship or two) that NK was not to be trusted.

• Written in 1960s and sometimes a bit (a lot!) paternalistic to 2019 ears. But compared to how his contemporaries probably wrote on what was very much a European-vs-Asian races context, I got a lot of grudging sympathy and respect for the North Koreans and Chinese fighters. Maybe less sympathy for Communism itself but that's fine by me.

Question:
The reason for the stalemate of the korean war.

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Short Answer:

The United Nations forces did not enjoy overwhelming Military Advantages in the Korean War.

The UN forces had no answer for the Soviet T-34(medium tank) initially in the Korean war.

US Army War College: The Armor Debacle in Korea, 1950: Implications for Today
Posted into position north of Osan, the Americans met the advancing enemy on the morning of 5 July. At 0800 hours, the six howitzers began firing on eight Russian-built T-34 tanks that were bearing down on the task force positions. The tanks were impervious to the artillery fire, and recoilless riffle and bazooka fire also had no effect. Within two hours, 33 North Korean T-34 tanks had passed through the American Positions, while Task Force Smith had been able to damage only two of the attacking tanks. A second wave of tanks cut through Task Force smith an hour later, and at 1145 hours three tanks led the 16h and 18th Infantry Regiments of the North Korean 4th Division in an assault on the American infantry positions, routing them.

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Battle of Osan
The Battle of Osan was the first U.S. ground action of the war. The fight showed that American forces were weak and unprepared for the war; outdated equipment was insufficient to fight North Korean armor and poorly trained and inexperienced units were no match for better-trained North Korean troops1 – though the disparity in number of troops engaged certainly had a profound effect on the outcome of this and future battles. Undisciplined U.S. troops abandoned their positions prematurely, leaving equipment and wounded for North Korean troops to capture.36 Smith also said he felt he had stayed too long in his position, allowing North Korean troops to envelop the force and cause heavy casualties as it retreated.1 These weaknesses would play out with other U.S. units for the next month as North Korean troops pushed them further back..... Over the next month the 24th Infantry Division would fight in numerous engagements to delay North Korean forces with similar results. Within a week, the 24th Infantry Division had been pushed back to Taejon where it was again defeated in the Battle of Taejon.6 The North Koreans, overwhelming U.S. forces time and again, were able to push the Eighth Army all the way back to Pusan,

The North Koreans and Chinese had thousands of T-34s and it remained a competitive tank through out the war.

Similarly Soviet MIG-15 was the best fighter of the Korean war and was often flown by experienced Soviet Pilots.

• Faster
• Quicker
• More maneuverable
• With a higher ceiling

than any American fighter until 1953 when the war was almost over. Head to Head: MiG-15 vs F-86 Sabre

Mikoyan-Gurevich MiG-15
The British Chief of the Air Staff said "Not only is it (Mig-15) faster than anything we are building today, but it is already being produced in very large numbers [...] The Russians, therefore, have achieved a four year lead over British development in respect of the vitally important interceptor fighter".

3 years lead over the US (see F-86f variant in the detailed answer).

The United States military which experienced a massive drawdown after WWII (US army was reduced to 7% the size from it's WWII peak in the 5 years from 1945-50)... was a shadow of it's former self. (See Detailed Answer).

Stalemate accurately describes only the last phase of the War after both sides had chased each other down and up and down and up again the Korean Peninsula. Seoul changed hands 4 times.

The stalemate phase was entered only after 4 key events occurred.

1. Nov 1950, China committing 380,000 man force to reverse UN gains after Inchon. Prior to this China's direct involvement was clandestine and the subject of debate, most notable by General MacArthur. With this act China's direct involvement was no longer in debate, and this brought the Soviet's retaliatory actions in Europe backed by the Soviet Bomb into direct focus.
2. Jan 1951, The UN forces now significantly south of their previous positions, had somewhat recovered from the massive Chinese offensive of Nov and were again on the offensive. This time by a new commander in General Matthew Ridgeway with new tactics and a new overall strategy. ( US General Walker, pervious commander of the American 8th Army is killed in a traffic accident Dec 23, 1950)
3. Mar 1951, UN forces had recaptured Seoul for a second and final time, along with most of the other South Korean territory still under Communist control.
4. April 11, 1951, General Douglas MacArthur is fired for publically criticizing President's Truman's strategy of stalemate. Leaving General Matthew Ridgeway who previously had been commandeer of the 8th Army Corps in overall command of UN Forces in Korea.

Only then did UN forces settle into a stalemate defensive war. Prior to these events, the war was quite active with both sides nearly destroying the other before each experiencing reversals.

The stalemate phase was a strategy dictated by global concerns. It was designed to block/deter communist expansion while minimizing the chance of a broader global or nuclear conflict. The word for this cold war strategy of stalemate was called Containment.

More Detailed Answer

While the "stalemate" statement accurately represents the end result and final phase of the Korean War beginning March of 1951, after UN operations designed to recapture South Korean territory still in Communist Hands:

• THUNDERBOLT
• KILLER
• RIPPER
• RUGGED

Stalemate doesn't represent the entire war especially the first 9 months which were the most active period. The first 9 months which displayed significant shifts in advantage for both sides. Before MacArthur's landing at Inchon the North Korean forces had pushed the United Nations forces to a small perimeter on the south eastern coast of the Korean peninsular. The Pusan Perimeter Aug 4 – Sept 18, 1950.

By Oct of 1950, UN Forces largely due to MacArthor's landing at Inchon, had turned the corner. Pushing nearly to the Yalu River the Korean border with China. China's "intervention" with 380,000 man force at the Ch'ongch'on River and Chosin Resevoir pushed the UN Forces south back below Seoul.

General MacArthur is fired by President Harry Truman largely for publically disagreeing with Truman over containment. Douglas MacArthur, who's landing at Inchon had initially changed the war for the UN and who politically had the clout to influence policy in Washington. MacArthur was a WWII hero, and a Presidential candidate in 1948 and 52, although he never got a party nomination. President Truman fired General MacArthur largely for vocalizing his opposition to Truman's containment strategy and Truman's approval rating after that (9 months after) dropped to 22%, the lowest Gallop approval rating ever polled for a sitting president.

3 December 1973 article in Time magazine, Truman was quoted as saying
I fired him because he wouldn't respect the authority of the President. I didn't fire him because he was a dumb son of a bitch, although he was, but that's not against the law for generals. If it was, half to three-quarters of them would be in jail.

Then with new leadership and a new strategy the UN forces cameback a second and final time only this time they did not advance (-)much beyond the 38th Parallel which designated the original border between the korea's.

(-) UN Forces actually went into North Korean territory some in order to occupy strategically more defensible positions. These lines north of the 38th Parallel were known as the

• Wyoming line, mostly about 10 miles north of 38th parallel.
• Missouri, 6-15 miles north
• Kansas mostly 10 miles north of 38th parallel.
• Jamestown Lines, stretched about 35 miles north of 38th parallel.

And were chosen to give the UN forces the advantage of more defensible positions for what was envisioned would be the coming truce.

The global policy adopted by the United States after WWII with regards to Communist Expansion can be summed up in 1 word. Containment. After MacArthur's advances after Inchon the US lost focus on this policy, partially because of MacArthur's confidence that China would not involve itself in the War. In Nov of 1950 however China committed a large army to defeat UN forces in Korea, ultimately leading to the dismissal of General MacArthur and the US recommitting to Containment strategy.

Containment
The U.S. followed containment when it entered the Korean War to defend South Korea from a communist invasion by North Korea. Initially, this directed the action of the US to only push back North Korea across the 38th Parallel and restore South Korea's sovereignty, thereby allowing North Korea's survival as a state. However, the success of the Inchon landing inspired the U.S. and the United Nations to adopt a rollback strategy instead and to overthrow communist North Korea, thus allowing nationwide elections under U.N. auspices.37 General Douglas MacArthur then advanced across the 38th Parallel into North Korea. The Chinese, fearful of a possible US presence on their border or even an invasion by them, then sent in a large army and defeated the U.N. forces, pushing them back below the 38th parallel. Although the Chinese had been planning to intervene for months,38 this action was interpreted by Truman's supporters as a response to U.S. forces crossing the 38th Parallel. That interpretation allowed the episode to be used to confirm the wisdom of the containment doctrine as opposed to rollback. The Communists were later pushed back to roughly around the original border, with minimal changes. Truman blamed MacArthur's focus on victory and adopted a "limited war" policy. His focus shifted to negotiating a settlement, which was finally reached in 1953. For his part, MacArthur denounced Truman's "no-win policy.

Question:
...the United Nations forces lead by the US held overwhelming military and technological superiority over the Chinese.

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US Army War College: The Armor Debacle in Korea, 1950: Implications for Today when the North Koreans invaded South Korea on 25 June 1950, the US Army had a sound doctrinal approach to war, but it did not have the forces to support the doctrine. One notable result was the destruction of Task Force Smith on 5 July 1950 by the tank-led North Korean Peoples Army.

Tanks and the Korean War: A case study of unpreparedness When the US Army went to war with Korea, it found itself unprepared to fight and win the first and succeeding battles. Hofmann argues that the unpreparedness was due to massive underfunding and poorly managed demobilization after World War II.

The North Koreans and Chinese had thousands of Soviets T-34 tanks. The T-34 tank was a superior tank to the majority of those of UN forces especially in the first six months of the war. The American WWII era M26 Pershing's and M24 Chaffee's were outclassed by the T-34. The M46 Patton was the first American Tank which compared favorable to the T-34 and it wasn't introduced until Late Dec 1950 and then only in limited numbers.

Worse, the Soviet built MIG 15 was the best fighter of the Korean war. The MIG 15 outclassed the American F-80 and F-84 fighters early in the war and could out climb, out accelerate, out maneuver and had a higher top speed than the F-86 Sabre which was introduced Nov 1950 to address the technological advantages of the MIG. The UN didn't have a comparable fighter to the MIG-15 until the introduction of the F-86(F) variant in 1953 when the war was almost over.

It's not accurate to say the United Nations forces held overwhelming military and technological superiority over the Soviet backed Chinese.

US Army War College: The Armor Debacle in Korea, 1950: Implications for Today While Eighth Army struggled to field armor formations, the Pentagon tried to field tank battalions that could be shipped to Korea......the third company was actually equipped with M-26 Pershing tanks that were sitting on concrete pedestals around the post at Fort Knox! These "monument tanks" were taken down from their mounts and shipped westward on 17 July 1950, along with the rest of the hastily formed battalion, less than five days after activation. The battalion landed at Pusan on 7 August 1950 and went straight into combat-"a complete bunch of strangers with no training.

To claim the United Nations forces were militarily superior or held military advantage over the Soviet Union, China, and North Korea was quite a stretch. While the 12 million man military the United States had fielded at it's peak during WWII (91 army divisions) accompanied by 71 aircraft carriers and 28 battleships included in it's 6,768 ship Navy and it's nearly 80,000 aircraft air-force maybe one could have made that claim. That peak WWII military was long gone in 1950. The US had a massive drawdown after WWII. In May of 1945 the United states had 12 million men under arms (8.5 million in the Army). by 1946 the United States army had been reduced to fewer than 1.5 million. By 1950 the United States army globally had fewer than 600,000 men. When President Truman told General MacAurther to use all forces available to him to relieve South Korea on June 30, 1950, MacAurther had very few combat ready divisions available to him. The divisions available to him were under strength and their mobility and firepower had been reduced by shortages of men and equipment.

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Korean War As an initial response to the invasion, Truman called for a naval blockade of North Korea, and was shocked to learn that such a blockade could be imposed only "on paper", since the US Navy no longer had the warships with which to carry out his request. Army officials, desperate for weaponry, recovered Sherman tanks from World War II Pacific battlefields and reconditioned them for shipment to Korea.[282] Army Ordnance officials at Fort Knox pulled down M26 Pershing tanks from display pedestals around Fort Knox in order to equip the third company of the Army's hastily formed 70th Tank Battalion.[285] Without adequate numbers of tactical fighter-bomber aircraft, the Air Force took F-51 (P-51) propeller-driven aircraft out of storage or from existing Air National Guard squadrons, and rushed them into front-line service. A shortage of spare parts and qualified maintenance personnel resulted in improvised repairs and overhauls. A Navy helicopter pilot aboard an active duty warship recalled fixing damaged rotor blades with masking tape in the absence of spares.

Timeline:

• May of 1945, Korea is divided into two countries per terms of WWII peace arrangements.
• Feb 1946, George F. Kennen at the request of the State dept writes the Long Telegram, on Soviet activities and countermeasures to be taken by the west. A key policy Kennen proposes, which would become US strategy throughout the cold war is Containment.
• Aug 29th, 1949, The Soviet Union tests their first Nuclear Bomb.
• June 25, 1950 North Korea Invades South Korea
• June 27, 1950 The United States Joins the Korean War
• June 28, 1950, First Battle of Seoul – North Korean captures Seoul

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• June 30, 1950, President Truman orders General MacArthur to use all forces at his command in the Pacific to relieve South Korea
• July 4th, 1950, The United States is defeated at Osan
• Sept 15th, 1950, MacArther lands at Inchon
• Sept 1950, Second Battle of Seoul – United Nations forces capture Seoul from the North Koreans, following the Battle of Inchon

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• Oct 1950, Chinese Troops joins the Korean War although MacArthur initially denies it.
• Nov 25, Dec 2 1950, Battle of the Ch'ongch'on River
• Nov 27, Dec 13 1950, Battle of Chosin Reservoir
• Dec. 23, 1950, US General Walker, commanding the American 8th Army dies in a traffic accidental Near Seoul. He is the second highest ranking American General in the War.
• Dec 26, 1950, General Matthew B. Ridgway, takes command of EUSA
• Jan 7, 1951, - Third Battle of Seoul – The Chinese People's Volunteer Army capture Seoul

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• Jan. 25, 1951, US Forces go in the offensive but this time with a limited objective to eliminate North Korean Forces from South Korea. Operations THUNDERBOLT, KILLER, RIPPER and RUGGED under General Ridgway carry the U.N. forces forward
• March 1951, Operation Ripper – United Nations forces recapture Seoul for the second and final time.

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• Feb 1, 1951, Peace Talks begin
• April 1951, General Douglas MacArthur is fired by President Harry Truman.
• April 1951, Fifth Battle of Seoul – The Chinese People's Volunteer Army attempt to recapture Seoul during the Chinese Spring Offensive but fails.

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• Nov 4, 1952, Dwight Eisenhower is elected President
• July 27, 1953, North and South Korea agree upon a truce
• April 1954, Talks at Geneva fail to Unite Korea.

Comments

From RS.29 This is rather one sided answer, that tries to mitigate the fact that US forces were soundly beaten by Chinese in the winter of 1950 , and that Chinese were in fact mostly light infantry force that held out vs superior firepower (something that for example Germans or Japanese could not do in WW2 ) . – rs.29

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I'm a little dumbfounded as to why you think my answer is one sided? I'm guessing because I state the UN forces strategy changed in late January of 1951, after General Matthew Ridgeway took command of 8th army corps and after China had pushed UN forces from near their border along the Yalu River beginning in Nov 1950 to south of the 38th parallel Jan 1951. When the UN forces returned to the offensive. That the new strategy did not call for rolling back communism in Korea but rather preserving the South Korean State by recapturing their territory and then fighting for statement. (aka containment ). But his thesis is well known and much debated even in 1950-51.

• Containment Korean War
• National Archives,
  Indeed, Asia proved to be the site of the first major battle waged in the name of containment: the Korean War.
• The United States Policy of Containment - The Korean War also inaugurated what became the U.S. policy of containment – the idea that communism could not be allowed to spread beyond a certain geographical point. Because the war was fought for political rather than military objectives, it quickly degenerated into a stalemate as both sides used the battlefield to jockey for political advantage at the negotiating table.

Facts are the West's leaders very much saw the Korean war as a piece of the global struggle with Communism. The west feared sparking a greater engagement globally with Communism, threatenning Europe and especially given the Soviet Union had the bomb. General MacArthur did not share this larger concern with the administration. To General MacArthur you fight wars to win, and anything less was not defendable. March 1951, MacArthur sent a letter to Joseph Martin, a senior House Republican leader who shared MacArthur’s support for declaring all-out war on China–and who could be counted upon to leak the letter to the press. “There is,” MacArthur wrote, “no substitute for victory” against international communism. For Truman, this letter was the last straw. On April 11, the president fired General MacArthur for insubordination. And it was all about whether UN forces should fight for all out victory rolling back communism, or whether they should fight for containment. Trying to minimize the risk of sparking an all out WWIII scenario.

As for tanks both China and North Korea had tanks in the Korean war. North Korea started that war with a well equipped highly trained professional army. They held many advantages over South Korean and UN forces as the early battle results testify too. Initially North Korean forces enjoyed a significant advantage in armor and equipment over both South Korea and UN Forces. Stalin outfitted the KPA with hundreds of modern tanks such as the T-34, as well as trucks, artillery, and small arms. It was South Korean which had no tanks either in numbers or level of advancement to match up against North Korea's equipment. North Korean 105th Armored Division was instrumental as part of their initial advance. Their 107th Tank Regiment, defeated the American Task Force Smith (Jul 5, 1950). The Soviet Union gave China 1,837 T-34-85 tanks. UN forces didn't have an equal tank to the T-34 until late in 1950, when the initial turbulent stage of the war was half over. When the first M46 Pattons appeared. The US M26 Pershing's and M24 Chaffee's fared poorly prior to that against the North Korean and Chinese T34 and their derivatives.

and that Chinese were in fact mostly light infantry force that held out vs superior firepower

Again I think that's a bit of a mischaracterization. The Chinese had massive numerical superiority and didn't just hold out but used that superiority to roll back the UN forces from their borders as I said pushing UN forces again down below the 38th parallel from the Yalu River on China's frontier. The Chinese also had armor, and artillery.

It's true that Matthew Ridgeway's eventual formula for dealing with china's numeric superiority in recovering from Nov 1950 offensives in late Jan, Jan. 25, 1951 was to coordinate his infantry movement with his artillery more closely. Ridgeway changed many of the tactical objectives of the war as well as supporting the overall strategy of containment which came from Washington better than MacArthur had.

From @jwenting
Sorry, but the Pershing was far superior to the T34, even the T34/85. Only real problem with the tank was that it wasn't available in any numbers. The Sherman was pretty similar overall to the Soviet design in combat effectiveness. Stopped reading after that obvious fallacy as it discredits everything that comes after.

Korean War Tanks, Fighting Vehicles, Specifications

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We are only discussing the t34/85 because that was the variant the soviets gave the North Koreans and Chinese

The Pershing was a heavy 46 ton tank good armor good gun. It’s problem was it was under powered at 10.9 horse power per ton.

Tanks of the U.S. in the Cold War
The mobility of the M26 Pershing was deemed unsatisfactory for a medium tank, as it used the same engine that powered the much lighter M4 Sherman.

The t34 was a medium tank at 35 tons with 15.9 horse power per ton ratio for example. T34 even giving up all that weight had a comparable gun 85mm vs 90mm and armor. T34 used sloped armor which was very innovative and influential and maximized protection for thickness. But the T34 had nearly twice the range and greater speed. The T-34 was a better tank, it gave up little and still had significant advantages.

Tanks of the U.S. in the Cold War
Being underpowered and unreliable in the mountainous Korean terrain, all Pershings were withdrawn from Korea in 1951, and replaced with M4 Shermans and M46 Pattons.

The Sherman and t34 were both medium tanks at 34.8 and 35 tons respectively. The Sherman however had less advanced armor a smaller gun half the range and significantly slower. The Sherman had no advantage over the t34 and significant disadvantages.

In general the Sherman in WWII had 1 world class advantage. It was easy to make and the US mass produced it. So while it was an inferior tank to the German Panthers and Tigers there were generally a lot of Shermans and they overwhelmed the German Tanks with numbers. The German tanks were harder to manufacture. The Sherman didn't even have that advantage over the t34 which was also built to be mass produced. In fact during WWII the Soviets produced more T-34s than the United States built Shermans. 49,324 Shermans to 57,300 T-34s

Based on the persistent comments by Hans, this new OP seems really keen to get an answer. So I will try. But I have a qualifier, and that is I'm not really that interested in rehashing political debates (which it could turn into, very quickly) on the Korean war. I'd rather delete this answer if that's the case.

Let's start with a timeline (Jun 25, 1950 – Jul 27, 1953), in the form of a really good set of maps of Korea:

Source: Hans van de Ven, "China at War - Triumph and Tragedy in the Emergence of the New China" (Harvard Univ Press, 2018)

It is obvious that the Korean war:

1. Started off somewhere close to 38th parallel.
2. Against North Korean army, by Sept of 1950, the UN forces, principally US 8th Army, came extremely close to being totally wiped out from the peninsula but the Pusan perimeter held.
3. Then the pendulum swung in the opposite, the US-led forces came essentially onto the Yalu River.
4. China then came into this war with a vengeance, pushing US-led UN forces back to 38th.

Relevance of these stages, and its context (below), should explain why the stalemate was the best option under the circumstance.

Next, allow me to do it this way, by explaining the counter-points of

• US Army's strength in Korean War,
• against the Chinese (after the 1st round with North Korean, supported by USSR), and
• finally, but most importantly, political will & troop morale.

US Army in Korean War: Doctrine & Mobility

• "US held overwhelming military and technological superiority over the Chinese" by OP in question

Answer: The US Army tactical doctrine changes after WW 2 were for greater combined arms (i.e. more infantry for tank divisions, and more tanks for infantry divisions). So, unless one is considering the nuclear (atom bomb) option, the mechanised & infantry divisions were generally useless in this theater of operations (mountain warfare) exactly because so much of post-WW2 doctrine was focused on tanks and European warfare.

The first part of the (Korean) war was thus charaterized by relatively mobile operations as the opposing armies swept up and down Korea. ... the Army expeienced difficulties with its doctrine. The combination of the terrain, weather and enemy tactics tended to hamper employment of much of the tactical doctrine and equipment of the Army which were oriented toward another world war that would be fought primarily in Europe.

Source: Major R.A. Doughty, "The evolution of US Army tactical doctrine, 1946-76" (Leavenworth Papers, Fort Leavenworth, Combat Studies, 1979), p.5.

The Chinese Communist Army

• Know Your Enemy

Answer: The US Army had been fighting the the North Korean Army (with Russian support), but once they reached Yalu River (3rd map, Nov 1950), they now encountered the Chinese which they had no experience with (Stilwell was with the Nationalists who lost against the Chinese Communist Army).

The failure to conduct proper defensive manoeuvre, after Nov 1950, was at the heart of the push-back by Chinese Army. Here's the problem:

The initial retrograde operation was especially difficult because of the hasty commitment of the ill-prepared units and because few Americans had ever participated in such an operation. In World War II, Americans had usually been on the offensive, and very few units had ever conducted a sustained defense. A 1954 study by the Infantry School discussed the initial difficulties with retrograde opera­tions in the Korean War and noted, “‘Many ... withdrawals were mob movements rather than military movements and the men were cut to pieces".

Source: Major R.A. Doughty, "The evolution of US Army tactical doctrine, 1946-76" (Leavenworth Papers, Fort Leavenworth, Combat Studies, 1979), p.8

But the US Army did adapt and innovate (more night operations against Chinese, better defensive positioning, etc.). But it was extremely costly just to get back to where they started, at 38th Parallel.

Morale and Will

• Why are we here? What are we fighting for?

Answer: This, ultimately, is the real reason for the stalemate. Why did UN and US forces fight this war? Why did the Chinese get involved once the US-led forces arrived at Yalu River?

The political will for liberal democracies (Cold War, ideological values, etc) may seem sufficient for UN and US forces, but the why for America and UN Forces was not even close to why the Chinese fought.

In Mao's mind, and the communist army, it was for their very existence (Chinese civilisation). Some in the West consider the Chinese War of Resistance against the Japanese (WW2 to the West) and the Civil War as separate issues. It wasn't to the Chinese. Some see end of WW2 in 1945 as the end of hostilities. Again, it wasn't. The Huaihai Campaign ended in early 1949, less than 18 month before Korean War broke out.

To the Chinese Army, the Korean war was the last and final phase of the past 15 years, beginning with (1) War of Resistance (against Japanese) in 1937, (2) war against the Nationalists until 1949, and (3) war against western imperialists (US-led UN forces), 1950-2/3.

The stalemate was achieved by July 1951. How much blood and treasury should America commit, again, to fight China to get back onto the Yalu River? Remember, the first time to the Yalu River was against the North Koreans. This next round, it was the Chinese. So, America chose to hold the line at 38th parallel instead of committing itself to another round. And that's where the line has stayed.

Given all these, I hope it should be obvious stalemate was the best (in my mind, the only) option.