Napalm is a military idiom designating a special type of aluminum soap used as a gelling agent of compatible volatile petrochemical (usually gasoline (petrol), kerosene and diesel fuel), used as an incendiary mixture. The name is a portmanteau of two of the constituents of the original thickening and gelling agents: aluminium naphthenate and aluminium salts of coconut fatty acids under the trade name aluminium "palmitate". Fuels thickened by the napalm are referred to as "napalm" simply. Any thickened fuel is often referred to as napalm, even if it doesn't contain aluminium salts. Aluminium soaps that form thermally stable gels are referred to as "napalm-type". Napalm B (Alecto) is the more extreme version of napalm and, although distinctly different in its chemical composition, is often referred to simply as "napalm". M4 is the successor of the napalm, is the standard A thickener of the US Army.
The first military-grade thickener based on aluminium soap, X-104 soap, simply called napalm and thickener M1, developed by Fieser's group and by Mr. Arthur Minich. This soap was the only standard thickener used on a large scale in WWII, the Korean War and the Vietnam War, with the minority, during the Vietnam war, being composed of Alecto, isooctal, instantgel and Incendagel. The sample 104 was extensively researched and investigated, becoming the 104 series (X-104 series).
A team led by chemist Louis Fieser originally developed napalm for the United States Chemical Warfare Service in 1942 in a secret laboratory at Harvard University. Of immediate first interest was its viability as an incendiary device to be used in firebombing campaigns during World War II; its potential to be coherently projected into a solid stream that would carry for distance (instead of the bloomy fireball of pure gasoline) resulted in widespread adoption in infantry flamethrowers as well. Acting as an anti-mist agent, napalm delays the evaporation of non-polar substances (hydrocarbons), extracted from oil.
Napalm burns at temperatures ranging from 800 to 1,200 °C (1,470 to 2,190 °F). In addition, it burns for a greater duration than gasoline, as well as being more easily dispersed and sticking tenaciously to its targets. These traits make it extremely effective (and controversial) in the anti-structure and antipersonnel role. It has been widely used in both the air and ground role, with the largest use to date being via air-dropped bombs in World War II (most notably in the devastating incendiary attacks on Japanese cities in 1945), and later close air support roles in Korea and Vietnam. Napalm also has fueled most of the flamethrowers (tank, ship and infantry-based) used since World War II, giving them much greater range, and was used in this role as a common weapon of urban combat by both the Axis and the Allies in World War II. Multiple nations (including the United States, China, Russia, Iran and North Korea) maintain large stockpiles of napalm-based weapons of various types.