Aside from Dresden, another German city that was essentially destroyed in a single series of air raids, and was likely an inspiration for the Economist comments, was Hamburg. Estimated deaths were around 40,000. The bombing of Hamburg was the first air raid that resulted in a firestorm: a fire so widespread and so large that it creates hurricane force winds that pull anything nearby into the fire. Firestorms are so intense that they suck the oxygen out of bomb shelters, so taking cover is not protection. Dresden also experienced a firestorm... much of the destruction of Dresden was the result not so much of the bombs, but the firestorm that resulted. In both Hamburg and Dresden, the fire burned itself out eventually, as a firestorm is essentially impossible to extinguish.

In the Pacific, Japanese cities were particularly vulnerable to fire attack, culminating in the single most destructive air raid on a city, the fire raid on Tokyo on March 9-10, 1945. 16 square miles of the city were destroyed (about four times the area destroyed by the atomic attack on Hiroshima), with death estimates between 100,000 and 130,000.

Area bombing of a city, rather than specifically targeting military and industrial areas, became a policy of the RAF, partially because the night bombing they favored was not particularly accurate. Later in the war, weapons production was scattered across many small cottage industry sized operations, so area bombing was the only practical way to attack those.

Given that a number of British cities had been bombed by Germany earlier in the war, and the V weapon attacks later in the war were very indiscriminate, there may have been a retribution aspect as well, although this was never codified as an official explanation.

Harris's stated reason for area bombing was to demoralize the population. Ironically, the British should have known that this goal wasn't achievable, for the simple reason that German bombing had not demoralized their population. If anything, the blitz made them angry.

Note also that towards the end of the war, the area bombing of German cities began to draw widespread criticism as unnecessary and uncivilized. After the war, Harris was was not awarded a peerage, which had been granted to all other officers of similar high rank, a snub that was attributed to the revulsion felt by the British public towards area bombing immediately after the war. Harris had been a primary proponent of area bombing during the war.

The Economist comments tend to reflect that sentiment.

TL; DR^*

• The article is referring to all the German cities destroyed by the allied strategic bombing campaign.
• Those bombings were not indiscriminate, but targeted (within the limitations of the technology of the day)
• They were carried out in accordance with the legal framework (Geneva and Hague Conventions) that governed the conduct of war at that time.
• The evidence actually suggests that Dresden was a legitimate military target, and that the bombing in February 1945 - while undoubtedly a terrible tragedy - was neither a war crime nor a crime against humanity.

The Question

Let's begin with the main question. The Economist article you cite is referring to the allied strategic bombing campaign.

The answer to your question:

What cities does the highlighted part refer to?

is straightforward: "pretty much all of them". There were few towns and cities in Germany that escaped unscathed from that campaign.

Now, it is worth reading that quote from that Economist article in context:

"Nor should the Western world console itself that the Russians alone stand condemned at the bar of the Allies' own justice. Waging aggressive war is the chief count in the indictment, but it is not the only one. Among crimes against humanity stands the offence of the indiscriminate bombing of civilian populations. Can the Americans who dropped the atom bomb and the British who destroyed the cities of Western Germany plead "not guilty" on this count?"

Which begs the question, was the allied strategic bombing campaign really the

"... indiscriminate bombing of civilian populations"?

Were the bombing raids targeted or indiscriminate?

While there were some RAF units that trained for specific precision bombing raids (like 617 Squadron, for example), the practical limitations of the technology of the day made it almost impossible for most units to deliver anything like precission bombing.

By 1942, the RAF could use the Gee radio navigation system to locate German towns and cities. Pathfinder squadrons could fly ahead of the main force and attempt to mark targets within those towns and cities for the main bomber force.

However, bombs falling from 14,000 feet were subjected to buffeting by winds and air currents for a long period as they fell. The analogue computer bomb sights of the 1940s had no way to compensate for this problem. Add to this the problems of cloud cover over the target, enemy anti-aircraft fire, searchlights, night-fighters etc., and it is hardly surprising that most bombs actually missed their targets.

Since it was effectively impossible to consistently hit anything more precise than whole areas of cities, many of the bombs dropped by the allies did hit civilian areas. But we must recognise that the civilians in those areas were not the target of the missions.

However, planners in the Air Ministry were happy to take advantage of the collateral damage from these raids and its effect on the morale of those civilian populations. An Air Staff paper, dated 23 September 1941 had defined the aim of attacks on urban centres in the following terms:

“The ultimate aim of the attack on a town area is to break the morale of the population which occupies it. To ensure this we must achieve two things: first, we must make the town physically uninhabitable and, secondly, we must make the people conscious of constant personal danger. The immediate aim, is therefore, twofold, namely, to produce (i) destruction, and (ii) the fear of death.”

(Also quoted in an extract from the official account of Bomber Command by Arthur Harris, 1945 (National Archives Catalogue ref: AIR 16/487)

Thus the evidence shows that while the bombing was targeted, and not indiscriminate, the effects on civilian populations were recognised - and even welcomed - by military planners during the war.

So was this legal?

The legal position

The fundamental problem was that the treaties that governed th conduct of nations at war had simply failed to keep up with the technology of the day.

The first Geneva Convention was adopted on 22 August 1864. Future agreements and conventions built upon this beginning.

By 1939, the key treaties that governed the conduct of war were the Hague Conventions of 1899 and 1907. Neither of these dealt with aerial warfare. (There had been an attempt in 1923 to forge an agreement for the Hague Rules of Air Warfare, but - for a number of reasons - this had failed.)

The result was that the only legal protection for towns and cities in 1939 was that given by the 1907 Hague Convention. Specifically

• Article 23 prohibited the destruction or seizure of the enemy's property, "unless such destruction or seizure be imperatively demanded by the necessities of war".
• Article 25 stated that "The attack or bombardment, by whatever means, of towns, villages, dwellings, or buildings which are undefended is prohibited".
• Article 27 stated that: "In sieges and bombardments all necessary steps must be taken to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected, provided they are not being used at the time for military purposes. It is the duty of the besieged to indicate the presence of such buildings or places by distinctive and visible signs, which shall be notified to the enemy beforehand."

(my emphasis)

And that was about it!

What this meant in practice was that international humanitarian law offered no protection against the aerial bombardment of civilian areas in enemy territory during World War II. It could not be illegal!

Your question explicitly mentions the example of Dresden, so I'd like to examine the evidence in a little more detail.

Dresden

Dresden is often cited as an example of an allied 'war crime'. As I explained above, it certainly couldn't be a war crime, as the laws governing aerial warfare and the aerial bombardment of cities simply didn't exist during the second world war. But was it a crime against humanity?

Did the raids on the City of Dresden on 13/15 February 1945 amount to the indiscriminate bombing of a civilian population?

]

"Dresden, partial view of the destroyed city center on the Elbe to the new town. In the center of Neumarkt and the ruins of the Frauenkirche." [Image source Wikimedia commons]

It is certainly true that Winston Churchill was troubled by the raid. There is no suggestion that he considered the raids to be either a war crime or a crime against humanity, but it is clear that he felt the raids undermined the allies claim to moral superiority over the axis powers. In a memorandum to the Chiefs of Staff Committee and the Chief of the Air Staff dated 28 March 1945, Churchill wrote:

"... The destruction of Dresden remains a serious query against the conduct of Allied bombing. I am of the opinion that military objectives must henceforward be more strictly studied in our own interests than that of the enemy."

Now, a cynic might reasonably make the observation that Churchill was a consumate politician who would have been aware of the contoversy that would surround the raids, and so would want to distance himself from them. Indeed, that may well actually be true. In any event, the bombing of Dresden did mark a turning-point in the allied strategic bombing offensive against Germany.

In recent years, some historians have gone further. Donald Bloxham, for example, argued that the bombing of Dresden actually constituted a war crime. Bloxham presented his case in Chapter 9 of Firestorm: The Bombing of Dresden 1945().

His argument appears to have three main points at its core:

1. Dresden was an historic city of little or no military importance.
2. Insufficient efforts were made to protect the civilian population.
3. The war was almost over, so the bombing was unnecessary anyway.

In fact, the first two questions were examined in some detail, first by an inquiry conducted at the behest of U.S. Army Chief of Staff, General George C. Marshall, and later by the US Air Force Historical Division (USAFHD). The Marshall report analysed the circumstances of the raid, and stated the raid was justified by the available intelligence [Taylor, 2004, p196]. The U.S. Air Force Historical Division report similarly concluded that the raids were militarily necessary, and fully justified, based on the following points:

• The raid had legitimate military ends, brought about by exigent military circumstances.
• Military units and anti-aircraft defences were sufficiently close that it was not valid to consider the city "undefended."
• The raid did not use extraordinary means but was comparable to other raids used against comparable targets.
• The raid was carried out through the normal chain of command, pursuant to directives and agreements then in force.
• The raid achieved the military objective, without excessive loss of civilian life.

So, considering the evidence, was Dresden really a city of no military importance?

In short, no. In his 2004 book, Dresden: Tuesday, 13 February 1945, Frederick Taylor observes that:

According to the 1944 handbook of the German Army High Command’s Weapon Office, the city of Dresden contained 127 factories that had been assigned their own three-letter manufacturing codes by which they were always referred to (for example, Zeiss-Ikon = dpv; Sachsenwerk = edr; Universelle = akb). ... An authority at the Dresden City Museum describes the handbook's code list as 'very incomplete', and it did not include smaller suppliers or workshops that were not assigned any codes. Dresden was ranked high among the Reich’s wartime industrial centres.

• [Taylor, Frederick, Dresden: Tuesday, February 13, 1945, Harper Collins, 2004, p148]

The military equiment being manufactured in Dresden in February 1945 included parts for the V1 'Doodlebug' flying bomb and the EZ 42 gun-sight which was to be used on the Me 262 and the He 162 [Uziel, Daniel, Arming the Luftwaffe: The German Aviation Industry in World War II, McFarland, 2012, p256].

Indeed, the 1942 Dresdner Jahrbuch (Dresden Yearbook), quoted by Taylor in the book cited above made the point explicitly:

Anyone who knows Dresden only as a cultural city, with its immortal architectural monuments and unique landscape, would rightly be very surprised to be made aware of the extensive and versatile industrial activity, with all its varied ramifications, that make Dresden one of the foremost industrial locations in the Reich.

• [ibid]

So it seems clear that these industrial plants were legitimate military targets.

Furthermore, Dresden was a vital link in the German rail network. In February 1945, 28 military transports a day passed through the city transporting troops ans tanks to the front line. These railway lines, and their associated transport infrastructure, also made Dresden a legitimate military target.

In addition, we know that Dresden had been designated as a defensive military strong-point against the Russian advance from the east by the German High Command. Once again, this would make the city a legitimate military target.

The anti-aircraft batteries in and around the city meant that it was not 'undefended'.

So there are good reasons to argue that the city was a legitimate military target. While the RAF and USAF might do their best to target only those areas of the city that were military objectives, the technology of the day meant that in practice much of the city would be destroyed.

But is it reasonable to argue that the war was almost over, so the bombing was actually unnecessary?

Well, certainly given 20/20 hindsight one might try to make that case (indeed, many have done just that). But in February 1945 I suspect that the situation would have appeared much less clear.

The allies had suffered significant casualties during the Battle of the Bulge which had ended just a few weeks earlier. German jet fighters like the Messerschmidt ME 262 remained a threat in the air, with the potential to change the balance of power in the battle for air superiority over Europe. V1 flying-bombs and V2 missiles were still falling on southern Britain and the areas of Europe liberated by the allies.

Viewed from that perspective, it might well have been far from obvious that the end of the war was imminent. Indeed, when seen from that perspective it would probably have been regarded as gross negligence not to have attacked a strategic target like Dresden, where the military objectives might significantly degrade the effectiveness of the German military machine, and in doing so, shorten the war.

Conclusion

So, going back to the article in The Economist and the question:

"Can the ... British who destroyed the cities of Western Germany plead "not guilty" on this count?"

I think on the evidence presented here, the answer to that question would be "yes".

^{TL; DR - "Too long; Didn't read}

There was in fact a general Anglo-American bombing campaign against German cities late in the war which we (or at least I) don't often hear about. However, it was carried out within the Geneva Conventions of the day.

It should be noted here that the American part did exist too. The entire European bombing campaign was generally a coordinated effort, with Americans taking the daylight runs, and the UK taking the nighttime runs. I suspect the person in question left the Americans out of the second part of his counter-indictment only because he'd already felt like they were adequately included in the first part. This was not a "British" campaign, it was an Allied campaign.¹ Any modern attempts to portray it as a wholly British activity seem quite suspect.

Not only was Dresden not alone, by the RAF's accounting it didn't even make the top 10 of most destroyed German cities. In order, those would be Bochum (83%), Mainz (80%), Hamburg (75%), Kassel (69%), Hagen (67%), Düsseldorf, Mannheim (both 64%), Cologne, Dessau (both 61%), Hanover, Bremen (both 60%). In terms of sheer area destroyed, Hamburg was far and away the "winner".

And yes, the historical record is that, while there were good practical effects on German weapon production, part of the intent of all this was terror.

Here's an excerpt from a declassified war dispatch from Sir Arthur Travers Harris, Chief of RAF Bomber Command during the period in question:

The ultimate aim of an attack on a town area is to break the morale of the population which occupies it. To ensure this, we must achieve two things: first, we must make the town physically uninhabitable and, secondly, we must make the people conscious of constant personal danger. The immediate aim, is therefore, twofold, namely, to produce (i) destruction and (ii) fear of death.

Here's a picture of what Cologne looked like in April of 1945.

None of this was really against the Hague Warfare Conventions of the day. The only serious practical restriction in place at the time was that you were supposed to try to avoid hitting things like hospitals and cathedrals². Notice in the above photo of destruction that the Cathedral is still standing. That shows you they were in fact making an effort to follow the conventions. Deliberate indiscriminate attacks on civilians were not explicitly outlawed until 1977.

^{1 - I suppose you could argue Stalin's Russia wasn't directly participating, but he was certainly aware it was going on, and I have trouble seeing where he'd have been anything less than encouraging about it.}

^{2 - This helps explain the odd line "Nobody steps on a Church in my town" from 1984's Ghostbusters. The people who wrote that movie were of an age where destroying a church was The Line for war crimes, but young enough to appreciate that this was a silly place to draw the line.}