Was any stimulant used in wars before WW2 that gave a significant advantage to soldiers?

KOLA NUTS

In sub-Saharan Africa, kola nuts have long been used by soldiers. For example, in the Sudan,

Military officials dispensed kola to their soldiers before battle. It was thought to make men brave, even eager for combat (‘Yana sa mutum ya yi yaki da yawa’), and it combated cowardice and the urge to flee on the battlefield because it made men tough

Source: Paul E. Lovejoy, 'Chapter 5' in Jordan Goodman, Andrew Sherratt, Paul E. Lovejoy (eds), 'Consuming Habits: Drugs in History and Anthropology' (2005)

Kola nuts are chewed and contain the stimulants caffeine, theobromine and kolatin.

Of the two most common varieties, Cola nitida contains from 1. 0 to 4.0 per cent caffeine by weight and traces of theobromine, while C. acuminata has from 1.5 to 3.6 per cent caffeine and 0.02 to 0.09 per cent theobromine. Both caffeine and theobromine are alkaloids which stimulate the nervous system and the skeletal muscles. Both varieties also contain small amounts of kolatin, a glucoside heart stimulant, and tannin.

Source: Lovejoy

Kola nuts are mildly addictive and were also used in many other ways (e.g. in ceremonies, as currency, as an aphrodisiac), especially in the Sahel region (between the desert and forest zones) of West Africa where the dominant religion, Islam, discouraged the use of other stimulants.

Until the 20th century, kola was very expensive and was thus often given as a gift by local aristocracies (or by military commanders to their soldiers). In modern West Africa, kola is much more affordable. It is commonly used, for example, by manual labourers.

Caffeine is a stimulant and it was heavily Used in the US Civil War. At the time, it was believed to “[give] a significant advantage”:

Grinspan states that Union General Benjamin Butler was aware of the effect caffeine had on soldiers and ordered his men to carry coffee in their canteens. He planned his attacks, in part, when his men were most caffeinated. Butler told a senior officer prior to a battle in October 1864 that “if your men get their coffee early in the morning, you can hold.”

While not describing it’s use for combat effectiveness, this article gives a brief history of coffee usage in the US Army

We tend to ignore coffee’s stimulant effects in discussions like this because it is safe to consume and legal. That does not mean that it has no effect.

FC: What exactly is a 'stimulant'? We might follow some modern definition and arrive at a certain restricted subset of chemicals that includes meth and modafinil. But that excludes quite a bit of drugs used and disregards a lot of effects that derive from synergistic combinations, timing, dosage set and setting of using drugs. The question also leaves open whether direct pharmacological effects are the only qualification needed or allowed; or whether indirect effects also count.

For example, ritalin is classified as a stimulant, yet in hyperactive children its outwardly observable effect at correct dose is of a 'calming' nature.

Therefore, the amount and number of substances used in warfare for their actual effects or even just their believed effects has to be much larger. A small collection:

Most probably and famously you might think of plain alcohol? Not using beer but wine and spirits can make most men quite violent and aggressive. (Modern beer might work similarly, but the almost universal inclusion of sedating and testosterone-countering hops makes it much less effective for 'aggression')

Some may wonder: Why even think about alcohol, which is usually classified as 'depressant', when the questions asks about stimulants? Some basics.

Alcohol produces both stimulant and sedating effects in humans. These two seemingly opposite effects are central to the understanding of much of the literature on alcohol use and misuse.

One famous example is found in Homer: nepenthes the drink of oblivion was most probably a mix of alcohol and opium, later known under the name of laudanum. Also in that work we find reference to the lotophagi, people addicted to lotus plant products (exact species unknown, perhaps literary overstated, but modern specimens do contain a range of psychoactives…)

Since the Columbian exchange there was also nicotine around the battle fields of the old world, suppressing some of the boredom that soldiering brings along, and providing a small kick for the tobacco smoke 'drinker'.

But if you work with some definition of drugs that excludes these two:

Older recipes of beer come to mind, and tend to take it over. Grutbeer would be one example, but the most well fitting description is "soldiers going berserk"?

Berserkergang:

Alcohol, fly agaric (or perhaps more likely Amanita pantherina) and henbane (among others) amplify the aggressiveness and disinhibition alcohol provides. Sometimes quite over the top.
That mushroom-fortified troops were seen on the battle field seems to be as recent as Siberian Soviet troops during the Battle of Székesfehérvár in Hungary in 1945.

Then we have the seemingly opposite, Assassins, being (supposedly?) motivated by glimpses of paradise due to their commanders giving them hashish in copious amounts… (Somewhat contested is the actual use of the drug by them and even more so the etymology. What is not contestable is that the drug itself does not increase aggressiveness and 'stoned' operatives are often more of a liability than an asset of assassins' plans. The point being that most accounts describe it as being given to them for (advance or later) reward and motivation. And actually, heavy THC use induces aggressiveness on sudden withdrawal…)

India has been called the world’s first cannabis-oriented culture. Ayurvedic (Hindu) and Tibbi (Islamic) practitioners gave it orally […] Ordinary Hindus and Muslims used it as a folk cure and to ward off boredom and fatigue, particularly during the harvest. Warriors drank bhang to steel their nerves; mendicants to concentrate their prayers; newlyweds to stoke their ardor. Cannabis was a cheap and popular aphrodisiac, given even to mares before they were mated.
_{— David T. Courtwright: "Forces of Habit. Drugs and the Making of the Modern World", Harvard University Press: Cambridge, London, 2001. (p40)}

Generally, if used, and that is: timed & dosed, correctly, anything can be made into some kind of 'soldier drug'.

Good old liquorice is a mild stimulant, especially in the morning, suppresses thirst, hunger, taste good, increases cortisol (fight or flight) and free testosterone — and was a standard marching provision in Macedonian, Roman, Napoleonic and Turkish armies. How 'significant' its advantages were may be of some debate, but its use was very widespread.

The ancient Chinese thought that licorice root imparted strength and endurance and consumed it mostly as teas. Licorice stores found in the tombs of Egyptian pharaohs including the 3000-year-old tomb of King Tutankhamen provide the earliest evidence of licorice use in Egypt. The root was placed in tombs for use in the afterlife to make a sweet beverage called mai sus, a ceremonial drink to honor the pharaohs that is still consumed in Egypt today 17. The ancient Greeks and Romans used licorice as a tonic and cold remedy. In Japan, the oldest specimen of licorice introduced from China in the middle of the eighth century still exists in Shosoin, the Imperial Storehouse, in Nara.

In the fourth century BC, the Greek botanist Theophrastus, a contemporary of Aristotle, described the use of licorice as a thirst quencher, for the treatment of asthma, dry cough, and lung diseases, and in wound healing when mixed with honey. The armies of Alexander the Great and later the Roman armies were given licorice to quench soldiers’ thirst during long marches. In the first century BC, the Roman naturalist Pliny the Elder wrote about various uses of licorice including lozenges to clear the throat and to postpone hunger and thirst, and as a remedy for dropsy, for ulcerous sores of the mouth and genitals, and for bladder and kidney ailments.
_{— Salvador F. Sena: "Licorice and Laboratory Tests", in: Amitava Dasgupta & Catherine A. Hammett-Stabler (eds): "Herbal Supplements Efficacy, Toxicity, Interactions with Western Drugs, and Effects on Clinical Laboratory Tests", John Wiley & Sons: Hoboken, 2011.}

Sugar itself may be considered a a short booster drug, given its 'real' energy and serotonin and dopamine secretion stimulating effects. However short these may last. But if sugar is combined with chocolate which contains significant amounts of theobromine and fat, it can get as sustaining as to be labeled a "fighting food":

As such it was used for example in the Franco-Prussian war by the French troops, or in the First World War by the British. While some people are really into it and believe in its almost magical properties:

As a stimulant, in my personal opinion dark chocolate is superior to adderall, ritalin, coca leaves, coffee, guayusa tea, and several other legal and illegal drugs.^src

—curiously the Prussian army when invading Holland in 1787 found neither tea nor cocoa or chocolate of much use…

Beer drinking was high on their list. It had been confirmed as a Teutonic trait by the hero of Prussian militarism, King Frederick the Great (d. 1786), who had set out his views on the matter in his “Coffee and Beer” Manifesto of 1777, which was intended to dissuade Prussians from drinking infusions instead of brews:

“His Majesty was brought up on beer and so were his ancestors and his officers. Many battles have been fought and won by soldiers nourished on beer, and the king does not believe that coffee-drinking soldiers can be depended on to endure hardship or to beat his enemies.”

_{— Iain Gately: "Drink. A Cultural History of Alcohol", Gotham Books: New York, 2008.}

A strange year in which caffeine prohibition spread, and Frederick's propaganda labeled tea as Chinese dragon poison… although much of this motivation was probably coming from the brewer's lobby and mercantilistic theory.
In 1862 the Prussians changed their minds and exchanged the ethanolic spirits for coffee in standard rations for soldiers.

But if it is really about currently mostly sorted into illegal 'stimulant drugs', then look no further than Inca warriors, having access to Coca leaves…
One natural drug that never went out of fashion, but was discovered quite late by Europeans:

General William Miller, an English-born soldier who in the 1820s fought alongside the Peruvian army during Peru’s war of independence, realized that chewing coca leaves was an essential and effective means of increasing soldiers’ strength and resilience. During a campaign in 1824, he ordered his men to use coca and later reported his observations in a book entitled Memories of General Miller in the Service of the Republic of Peru.^(Kamienski)

Widespread European recognition of the effects came just shortly before: During the siege of La Paz in 1781 only the use of coca leaves enable the soldiers to endure the height, hardship and fighting. The siege force even sent back a significant portion of their people to get more of this from far away. But ironically it is said that also only the large stockpiles of it within the city enabled the besieged to hold out for so long when food supplies exhausted.

The isolated compound cocaine was then becoming really popular during the First World War:

Paradoxically, the First World War created an increasing demand for cocaine, but at the same time it caused a great disturbance in international trade, which significantly reduced the supply of raw materials and thus hampered the production of the drug. However, the decline of international trade in coca and cocaine made for the rapid development of one pharmaceutical company: Nederlandsche Cocaïne Fabriek Ltd. (NCF).^(Kamienski)

The notorious user Benn vehemently denied being a coke head later on, but freely admits that during his time in the trenches he had a time when he couldn't do without. But the trade embargo and the that time inofficial use curbed the overall effect.

That this was used in either Vin Mariani or even marketed for soldiering is self evident in this picture (which shows a synergistic combination with Kola):

_{— Src: Pills, spills and the peloton Since cyclists just love to dope up as much as soldiers in the Antarctic.}

Because Forced March worked so well during these extremely wearying expeditions, it is hardly surprising that the command of the British Army decided to try it out on the soldiers of the expeditionary force in Europe.

Given the addiction of epidemic proportions among the veterans of the First World War, there are reasons to believe that the conflict left hundreds of thousands of men addicted to cocaine. The combatants, particularly on the Western Front, were in all probability usually unaware of being given a white “boosting” powder mixed with food or drink. Based on her research Conny Braam concludes that British soldiers

“got a cup of rum before they went over the top and the cocaine might have been in the rum, because with alcohol it works doubly well. I think a lot of these soldiers had no idea.”
^{— Kamienski}

During the Great War The Nederlandsche Cocaïnefabriek upped their production:

originally produced an average of 14,000 kg of cocaine a year. But a surge in demand from military commanders after 1914 saw production rise to between 20,000 and 30,000 kg a year. And it wasn't expensive — one kilogram of cocaine cost 800 guilders on the open market. That's around 36 euro cents per gram, less than a hundredth of the price it goes for today.^(src)

How creative humans get when making and taking drugs is probably best illustrated in Massai warriors. In pre-WW1 times they were noted for ferocity and did use 10 different kinds of stimulants found in their surroundings.

— Arthur C. Lehmann & Louis J. Mihalyi: "Aggression, Bravery, Endurance, and Drugs: A Radical Re-evaluation and Analysis of the Masai Warrior Complex", Ethnology, Vol. 21, No. 4 (Oct., 1982), pp. 335-347.

A similar practice was observed in Zulu and Moro warriors.

While intelezi was believed to make the Zulus fearless warriors, a specially medicated beer was thought to provide them with extraordinary protection, allegedly making them more resistant to enemy attacks and fire.

In addition, the warriors received rations of dagga, the South African variety of cannabis, which initially after taking has a stimulating rather than sedative effect. Prior to combat they got drugged as a group either by smoking dagga, inhaling its fumes, or drinking a cannabis broth. Alfred T. Bryant, one of the greatest early twentieth-century authorities on Zulu history and customs, observed that the young warriors smoked dagga before an attack so that they were capable of accomplishing almost any feat.
_{— Lukasz Kamienski: "Shooting Up: A Short History of Drugs and War", Oxford University Press: Oxford, New York, 2016.}

Or in Kenya:

Samburu use a variety of herbal stimulants to give them "strength," but also for relaxation. Tobacco (I-kambau) is chewed […] The cocaine-like stimulant Catha edulis (VaW) End!. (mira'a or khat in Somali) is popular among men; it is grown in the highlands of Mt. Meru or Mt. Marsabit, and bought from sellers in towns.
Members of the warrior age-grade consume a variety of "strength-producing" soups, some of which are said to cause "shaking" (aduku) or "trembling" (nkirakirr), pronounced muscular spasms characteristic of Maa-speaking warriors during intense social situations including ceremonies and warfare. These plants include l-kinyil (Rhamnus prinoides L'Herit.), l-kitalaswa (Myrica salicifolia A. Rich.), and n-kilenyei (Syzgium cordatum Hochst.) (Spencer 1959).
_{— Elliot Fratkin: "Traditional Medicine and Concepts of Healing Among Samburu Pastoralists of Kenya", Journal of Ethnobiology 16(1):63-9, 1996}

In summary, the most important war drugs, as classically classified were alcohol, tobacco, opium, speed (the only decidedly modern one), coca, and caffeine. Coffee being a latecomer to the battlefields, Camellia sinensis became important much earlier. Although in China it was more significant in enabling Song China to increase their supply of horses through trade. Tea in Japan had slightly more direct influence on warfare through culture:

One description of the samurai code of honor known as bushido—the “way of the warrior”—noted that “a samurai whose only attribute is strength is not acceptable. He must use his leisure time to practice poetry and understand the tea ceremony. Toyotomi Hideyoshi (1536–1598), a peasant-turned-samurai warlord who rose to become Japan’s second great unifier after more than 100 years of civil wars, was as committed to mastering the art of the tea ceremony as he was to the military unification of Japan. Indeed, fancying himself a great tea master, he went so far as to insist on bringing a portable teahouse onto the battlefield. According to one account, “Hideyoshi would then calmly practice the tea ceremony in view of both his own troops and his enemies, inspiring confidence in the first and fear in the second.^(Andreas)

How much the directly stimulating and other mental effects of tea played out on these battlefields seems unclear.

In Europe coffee also propelled the Ottomans to the gates of Vienna. However, the drug alone did not led them really storming the city?

The most famous account of coffee’s journey west involved the failed Ottoman siege of Vienna in 1683, remembered as both the end of Ottoman imperial ambitions in Europe and the beginning of Viennese coffee drinking. When the siege was repelled, the retreating Turks left behind dozens of sacks filled with mysterious green beans that the locals mistook for camel fodder.
_{— Peter Andreas: "Killer High. A History Of War In Six Drugs", Oxford University Press: Oxford, New York, 2020.}

And I guess that closes the circle to the starting question: whether acute overdose or long-time abuse, not a single drug 'gave any army a significant advantage' in any war. If at all, only optimal use and that is dosage can increase a soldiers effectiveness. When the panzer-chocolate meth-fueled nazi tanks raced to the Channel coast, they also had to rest then, because no human can survive without sleep in even the short term run.

Note "Panzerschokolade" is really two things: a nickname for pervitin or crystal-meth used by German soldiers, just like amphetamine and ephedrine was used by British and Japanese soldiers. Also and more often used was the term Fliegermarzipan (flyer's marzipan). And it was/is also a designation for a real chocolate, 'Scho-Ka-Kola' introduced in 1935 and in 1936 advertised for the Summer Olympics as a sports-nutrition and performance enhancer, combining three stimulants:

coffee, cocoa and kola. Unlike methamphetamine, which army command eventually withdrew from supplies after medical worries, Scho-Ka-Kola was issued as long as possible.

If you want to eliminate fatigue with Pervitin, you can be sure that the collapse of your performance must come one day. That the remedy may be used once against fatigue for a high performance pilot who still has to fly two hours is probably correct. But it must not be used in every state of fatigue which in reality can only be compensated by sleep. This must be obvious to us as doctors.
_{— Doctor Conti, March 19, 1940, in Berlin, translated from a quote in Jens Alexander Steinat: "Ernst Speer (1889-1964) Leben – Werk – Wirkung", Dissertation, Eberhard-Karls-Universität zu Tübingen, 2004. (PDF)}

But if we want to look for a chemically and pharmacologically 'most close relative' to the US Army's now popular 'go-pills', then we can safely say that the Chinese 'had them' long ago:

Chinese sentries along the Great Wall took the herb ma huang (active ingredient: ephedrine).^(src)

Which has a history, going back a bit

3000 years ago Shen Nung tested this drug

and is even today used either directly as a weight-loss agent or precursor chemical for amphetamines and meth-like substances.

Coffee didn't conquer Vienna (for the Turks that is), Crystal Meth didn't take Moscow (for the Nazis, the drug now being a popular choice there as well). Coca didn't drive out the conquistadores and so on.

Drugs and warfare have always gone hand in hand – from Homeric warriors drinking wine and taking opium to Wehrmacht troops popping methamphetamines. The truth is, soldiers have been fighting while high for much of history.
_{— Łukasz Kamieński: "Combat High – A Sobering History of Drug Use in Wartime", MilitaryHistoryNow.com • 27 February, 2017}