The first use in warfare I’ve read is generally attributed to the Spanish Nationalists in 1936, but kerosene and glass bottles had been around long before then. It seems very strange to me that nobody before that point had the idea to make a simple firebomb of that design, when the materials were so commonplace.
It seems to be used on the battlefield primarily as an anti-tank weapon, which I originally thought was my answer (that there wasn’t a need for it because of the lack of tanks), but surely it is effective enough against infantry, and particularly structures, that that cannot be the answer.
First, a comment on modern use:
Why do we see Molotov cocktails used in riots and protests today, but much more rarely in the late 19th and early 20th centuries? There are two major reasons:
Molotov cocktails aren't very effective weapons, but they can produce spectacular video footage.
Modern police tend to be much more restrained than late 19th and early 20th century police.
The first of these means that Molotov cocktails feature heavily in TV news coverage. The second of these means that protestors/rioters have little fear of being shot for throwing Molotov cocktails. Before TV news coverage with video, spectacle was a less important motive. This removes much of the impact of Molotov cocktails in protests. Into the 1930s, police were more likely to use deadly force in response to provocations such as Molotov cocktails. Given the use of shotguns firing buckshot against unarmed protestors (e.g., the Minneapolis general strike of 1934), and revolvers against unarmed protestors (e.g., the Chicago Memorial Day massacre of 1937), it is very likely that in many countries, Molotov cocktails would have attracted prompt and potentially-deadly retaliation. At this point, we can note that Molotov cocktails are not very effective weapons - they have short range, and are slow enough when thrown so that they can be avoided. Some examples of Molotov cocktails having little effect:
In South Korea, Molotov cocktails were frequently used in riots for many years. There were some serious injuries from their use, and occasional deaths, but very few compared to the number of Molotov cocktails thrown. The Korean police usually acted with restraint, and did not use firearms - Molotov cocktails appear to have been part of the tacit rules of engagement. If the police were ready, willing, and able to fire on Molotov-throwers with guns, the examples of use above would have resulted in many dead and wounded protestors, with little or no injury to the police (this has happened in recent fighting in Myanmar). It is only restraints on violent response against protestors that makes Molotov cocktails a viable weapon in modern protests.
Next, the older history of such incendiaries:
Molotov-cocktail-like incendiary bombs are quite old. Before glass bottle were available (and often even when they were), earthenware or other ceramic containers were used. These were cheap and brittle, reliably breaking on impact. Such ceramic firebombs date to the early 1st millennium BC, if not earlier. The filling could be a flammable liquid, or gunpowder (which, if not confined, will burn rather than explode), or a flammable solid. Some examples of early fire grenades and similar incendiaries:
10th-12th century, Crete: https://commons.wikimedia.org/wiki/File:Liquid_fire_granades_Chania.jpg
13th century, Iran: https://commons.wikimedia.org/wiki/File:Pottery_Fire_Bomb_from_Iran.jpg
17th century, Europe: https://commons.wikimedia.org/wiki/File:Fire-Lime-Pots_Veste-Coburg_17th_Century.jpg
Other types of hand-thrown incendiaries include flammable balls, which could be soaked in flammable liquid, and/or use gunpowder:
Such bombs could be thrown slings or catapults, as well as being thrown by hand.
As noted above, Molotov cocktails are often not very effective anti-personnel weapons. It is likely that much of their use was against buildings and siege equipment. Often, against individual enemies, a javelin, arrow, crossbow bolt, or slingstone would be more effective, and could be used at longer range. Once the use of gunpowder was widespread, explosive grenades could be used, which would also be more effective. There is one important exception to the generalisation of Molotov cocktails being poor anti-personnel weapons: armoured soldiers. Armour tends to be designed to keep out those arrows and javelins, and firebombs offer an opportunity to bypass the armour. Jean de Joinville, in his The Life of St Louis describes such a use of a firebomb:
Finally, they brought up a peasant, who threw Greek fire at them thrice. Once William of Boon caught the vessel of Greek fire on his buckler, for if it had set light to anything on him, he would have been burnt. We were all covered with the fire-darts that missed the serjeants.
Containers of hot water and hot sand, and occasionally hot oil (the famous "boiling oil"), were also used, and could effectively bypass armour, without needing to worry about whether the firebomb contents catch fire.
This use against armoured soldiers is an early parallel to the more recent use of Molotov cocktails against armoured vehicles. Firebombs continued to be used against buildings and in sieges, but the introduction of armoured cars motivated their use against vehicles. For example, the IRA was using them against British armoured cars in 1922. As you note, the Spanish Civil War is often (and incorrectly) described as the first war to see the use of Molotov cocktails. They were not very effective anti-tank weapons - they rarely destroyed or knocked-out tanks. However, tank crews sometimes panicked when their tank was hit by a Molotov cocktail, and abandoned their tank - tanks were captured during the Spanish Civil War in this way. Generally, sufficiently large explosive charges were more effective anti-tank weapons. This continued to be the case - during the Winter War and Continuation War, Finnish soldiers used Molotov cocktails, but explosive charges were more effective. An instructive example of a police vehicle being hit by a Molotov cocktail, with much flame and little damage:
There is another disadvantage of Molotov cocktails: they are relatively dangerous weapons to use. As a Spanish Civil War International Brigade veteran wrote:
We in Spain had not always enough [anti-tank grenades], so we used "petrol bombs." I do not recommend these, and I mention them only with a serious warning. At least ten per cent, of those who try these nasty things are likely to burn themselves quite badly.
We made "petrol bombs" roughly as follows: take a 2-lb. glass jam jar. Fill with petrol. Take a heavy curtain, hail a blanket, or some other heavy material. Wrap this over the mouth of the jar, tie it round the neck with string, leave the ends of the material hanging free. ... Do not play with these things. They are highly dangerous.
Petrol is not nearly so good as a hand-grenade neatly placed by a man accustomed to using explosives.
For the full text, see:
To reinforce this warning, this appears to be a case of a protester catching fire from their own Molotov cocktail:
Finally, three related points of historical trivia:
1: Ceramic grenades (filled with conventional explosives) were manufactured as late as WWII (due to shortages of other materials):
2: The idea of the Molotov cocktail - a glass bottle filled with petroleum spirit (e.g., kerosene, petrol/gasoline) dates back at least to 1871. As the Paris Commune crumbled, and Paris was recaptured by government troops, many buildings burned. While the cause appears to have been conventional methods of arson, blame was popularly placed on pétroleuses, Communard women using Molotov cocktails. Some women were shot in the streets due to suspicion of being pétroleuses, and at least 13 women were arrested (but none found guilty).
3: The late 19th and early 20th centuries saw common use of "fire grenades". These were not Molotov cocktails, but rather the opposite: fire-fighting devices. The simplest type was a glass container full of salt water (salt water to avoid freezing in low temperatures), and others contained other substances to suppress fires (e.g., chemicals that would release gases that would suppress the fire). Their use is illustrated in this advertisement showing two rather nonchalant children extinguishing a fire while their much more agitated mother looks on:
For more on these (and the source of that ad), see:
Further reading:
For more on the history of petrol bombs, see:
