The recipe is simple: take an empty glass bottle, fill it with gasoline or other suitably flammable liquid, and stuff a piece of cloth – preferably also soaked in gasoline – into the neck. To use, simply ignite the cloth and throw. The quintessential improvised weapon, the Molotov cocktail has become a potent symbol of armed rebellion and violent protest the world over. But who invented this iconic weapon, and how did it get its unusual name?

While improvised incendiary devices have existed for centuries, the Molotov cocktail as we know it first emerged during the Spanish Civil War of 1936-1939, in which the right-wing Falangist forces of General Fransisco Franco fought left-wing Republican forces for control of the country. Franco’s forces, though equipped with the latest combat aircraft by its fascist allies Germany and Italy, were largely lacking in tanks and anti-tank weapons, while the Republicans, backed by the Soviet Union, fielded the latest Russian T-26 and T-28 tanks. The Loyalists were thus forced to improvise their own anti-tank weapons, including satchel charges – essentially shoulder bags filled with explosives – and petrol bombs. While flame might seem like an ineffective weapon against a tank, if a large enough fire can be started on the vehicle’s rear deck, it can starve the engine of oxygen and cause it to shut off, rendering the tank immobile and vulnerable. Most tanks of this era were powered by gasoline instead of the less-flammable diesel, so a fierce enough conflagration could also ignite the fuel tanks or ammunition stored inside the hull. Finally, smoke could be drawn by the ventilation fans into the crew compartment, suffocating the crew and forcing them to bail out. Loyalist forces used a wide variety of incendiary devices throughout the conflict, from the classic glass-bottle petrol bomb to blankets soaked in gasoline or kerosene thrown onto tanks from a high window.

However, the petrol bomb would not get its now-ubiquitous name until the Soviet-Finnish Winter War of 1939-1940. In the late 1930s, the Soviet government of Josef Stalin grew increasingly paranoid of the supposed threat posed by neighbouring Finland – especially to the strategically important city of Leningrad which lay only 32km from the Finnish border. In October 1939 the Soviets opened negotiations with Finland, demanding they cede territory along the southern end of the border in exchange for Soviet territory in Karelia to the north. The Finns refused, and on November 30, 1939, the Soviet Union invaded Finland.

The Soviets expected a walkover. Their invasion force of 760,000 soldiers, 6,500 tanks, and 3,800 aircraft faced a vastly inferior Finnish army of only 340,000 soldiers with hardly any tanks or airforce. But the Soviets had two major weaknesses. The first was Stalin’s great purge of 1938, which had decimated the Red Army’s officer corps. The second was the Finns’ superior knowledge of the land and their mastery of winter warfare. Though hopelessly outmanned and outgunned, through the use of highly mobile ski troops, ambushes, and hit-and-run tactics the Finns managed to inflict heavily casualties on the Soviets. Having few anti-tank weapons, Finnish troops relied on near-suicidal tactics like prying off a tank’s tracks using crowbars and the extensive use of petrol bombs. While early in the war these were improvised by the troops themselves, later examples were mass-produced by the government alcohol monopoly Alko at the distillery in Rajamäki. These bombs, some 450,000 of which were produced by the war’s end, consisted of a sealed 750ml glass bottle filled with alcohol, kerosene, potassium chlorate, and tar to allow the mixture to stick to the side of a tank. Instead of a fuel-soaked rag, for a fuze the bomb used a pair of wind-proof storm matches strapped to the sides of the bottle.

These weapon’s famous nickname came from an incident early in the conflict. On the opening day of the invasion, Soviet aircraft bombed the Finnish capital of Helsinki. Among the weapons they dropped was the RRAB-3, a 2-metre long cluster munition holding up to 60 smaller incendiary bombs. Fins on the rear of the bomb caused it to spin as it fell, flinging the submunitions out via centrifugal force and scattering them over a wide area. Facing worldwide condemnation over the invasion, Vyacheslav Molotov, the Soviet Foreign Minister, claimed that the Soviets were not in fact bombing Finland but rather dropping food aid to starving Finns. In response, the Finns began referring to the RRAB-3 bombs as “Molotov’s Breadbaskets.” In turn, petrol bombs came to be known as Molotovin koktaili or, “Molotov cocktails,” as “ a drink to go with his food parcels.”

Yet despite their heroic resistance, the Finns could not hold back the Soviet onslaught, and on March 13, 1940 the Finnish government signed the Moscow Treaty, ceding 11% of its territory to the Soviet Union. Nonetheless, the Winter War was an embarrassment for the Red Army, which had suffered casualties of over 167,000 dead and 207,000 wounded compared to the Finns’ 25,900 dead and 43,500 wounded.

Meanwhile, Great Britain was facing its own invasion crisis. Following the evacuation of the British Expeditionary Force from Dunkirk in June 1940, a German invasion of the British Isles appeared imminent. With only 40,000 regular troops remaining to defend the island, the government turned to the Home Guard, an organization of 1.5 million civilians otherwise ineligible for regular military service. While strong in numbers, the Home Guard was woefully ill-equipped, to the point that many members were issued sharpened sticks known as “Invasion Pikes” instead of rifles. To make up the shortfall in equipment, British inventors came up with a variety of ingenious and sometimes bizarre weapons which could be easily produced using common materials. Among these was a version of the Molotov cocktail known as the Grenade, Hand or Projector No. 76. Also known as the Allbright-Wilson Bomb or the SIP bomb – short for Self-Igniting Phosphorus – the No.76 consisted of a half-pint glass bottle sealed with a crown stopper, filled with a mixture of benzene, water, white phosphorus, and a strip of raw rubber. Over time the rubber would dissolve in the benzene and render it suitably sticky. When thrown against a target the bottle would shatter and the white phosphorus ignite on contact with the air, setting fire to the benzene-rubber mixture. Due to the highly-volatile nature of the white phosphorus, Home Guard members were advised to store the grenades in water in case the glass bottle broke.

Two versions of the SIP grenade were manufactured: a thin-walled version with a red cap for hand throwing and a thick-walled version with a green cap for use with the 2.5in Northover Projector, a crude mortar designed specifically for Home Guard use. The maximum range of an SIP grenade fired from a Northover projector was around 200 yards, though at this point the grenade would be tumbling so erratically that the chances of actually hitting a tank would be next to nil. British engineers also developed larger versions of the Molotov cocktail concept such as the Flame Fougasse, Demi-Fougasse, and the Hedge-Hopper. These consisted of a 50-gallon drum filled with gasoline and fuel oil and fitted with a guncotton propellant charge, which were hidden at crossroads and other ambush points. When an enemy vehicle approached the charge would be remotely detonated, launching the drum and covering the target in a sea of flame. By June 1941 nearly 7000 flame traps and 6 million SIP grenades had been manufactured and distributed to the Home Guard. Thankfully the feared German invasion never came and none were ever used in combat, though buried caches of them do still turn up from time to time – much to the chagrin of homeowners and construction workers.

The United States also produced an official Molotov cocktail, designated the M1 Frangible Grenade. Similar to the British SIP, it consisted of a small sealed glass bottle filled with various combinations of alcohol, gasoline, naphthalene, or napalm, ignited by white phosphorus or various chemical and mechanical fuzes. Versions were also made filled with chemical warfare agents such as cyanide and mustard gas. These were not intended for use by regular troops but rather for distribution to guerrilla groups in Japanese-occupied Asian countries. But like many such weapons few if any were ever used in combat and all stocks were destroyed at the conclusion of the war. For while cheap and easy to manufacture, Molotov cocktails are often as hazardous to their users as to the enemy, and have thus largely remained a weapon of last resort. Perhaps their most famous use during WWII was during the 1943 Warsaw Ghetto Uprising, when a thousand Polish Jews equipped mostly with improvised weapons bravely resisted Nazi attempts to liquidate the ghetto and deport its inhabitants to the extermination camps at Majdanek and Treblinka.

Since the Second World War, Molotov cocktails have been used in conflicts and protests too varied and numerous to list, the simple technology still proving highly effective despite significant advancements in tank design. During the 1956 Hungarian Uprising, for example, Hungarian freedom fighters managed to knock out some 400 Soviet tanks using only homemade petrol bombs. The weapon’s ultra-simple design makes it easy for even the most poorly-equipped fighter to construct using all sorts of materials. And we do mean all sorts. In 2017, protests against the Venezuelan government of President Nicolás Maduro saw the introduction of the amusingly named “Puputov cocktail,” which is just what it sounds like: a glass jar or bottle filled with faeces. On May 10, 2017, these weapons – along with jars of paint to block the windows of police vehicles – were widely deployed in a protest action known as La Marcha de la Mierda or Shit March. Thanks to this supreme simplicity and versatility, the humble Molotov cocktail will likely remain the preferred weapon of the underdog for decades to come.