In their tear-gassed standoffs with police in Ferguson, Missouri, some protesters have retaliated with the weapon of urban revolutionaries and improvisational militaries alike: the Molotov cocktail.

Easy and cheap to make, the Molotov cocktail is thought to have been invented during the Spanish Civil War, where it was used by the Republicans against Nationalist tanks. The original design was a mixture of tar, ethanol, and gasoline in a beer bottle, creating a substance that's both sticky and flammable; either an oil-soaked rag or a long, wind-proof match is inserted into the bottle’s mouth to act as a wick. When the "bottle bomb" hits its target, the sticky mixture of fuel and flame ignite, causing a large fireball and coating whatever it hits with fire.

But why is the weapon named after Vyacheslav Molotov, the Soviet foreign minister who signed the secret 1939 Nazi-Soviet non-aggression pact that heralded World War Two?

The answer comes from Finland.

The Molotov-Ribbentrop pact divvied Europe up into “spheres of influence,” carving Poland into Nazi and Soviet territory, while ceding Finland to the Soviets, who had previously controlled it under the Russian Empire.