An incendiary is a weapon which is specifically designed to inflict thermal damage on a target, usually by setting it on fire. When considered as a type of ammunition it will be called an incendiary round.
Like love, this definition covers a multitude of sins.
The most basic incendiary weapon is probably the burning brand or torch, used as flaming club against an opponent, and the first ranged incendiary a scoop of burning cinders from a fire. Primitive man almost certainly understood the uses of fire as a weapon before he had fully mastered it as a tool - perhaps a psychological weapon as much as one that caused real damage, but the ability of incendiaries to inspire fear remains a potent feature to this day.
Fire arrows and pots of burning coals served mankind for millenia, and burning pitch followed close behind where it could be had - indeed the first grenades on record were in fact ceramic pots of naptha (a sort of primitive molotov cocktail). Where there was no naptha to be had, pioneering weapon designers experimented with pine tar and distilled alcohol and other flammable substances, inventing greek fire at least once along the way. Once liquid fire had been developed it could be delivered by syphons and syringes and the flamethrower had been born. Greek Fire, or less advanced substances, could also be delivered by catapults and other siege engines, greatly increasing the incendiary capabilities of artillery, which had previously been limited to flinging burning solids.
The advent of gunpowder continued to widen the range of incendiaries - a use to which it seems to have been adapted before it was used as an explosive or propellant - the earliest description of a gunpowder weapon available, the Spear of Vehement Fire seems to be some kind of hand held flame jet rather than any truly ranged weapon.
Gunpowder artillery proved a bit lackluster in the matter of incendiaries - the carcass shot was developed, which was a metal cage containing burning material, but being short ranged, inaccurate and prone to disintegrate on firing it was not much loved. The other possibility was that of regular cannon balls warmed to red heat in a furnace before loading. Obviously this was not entirely safe around a weapon that was fed with loose gunpowder…
The early twentieth century lead to developements in chemistry that would revolutionise incendiaries - the industrialisation of substances such as magnesium, thermite and white phosphorous allowed the deployment of relatively stable incendiary munitions, and they were followed on a larger scale by napalm and its relatives.
Increasingly incendiaries have become the province of artillery (or at least heavy weapons) - whilst a fire arrow might once have delivered an acceptable payload, setting things on fire at range these days tends to require a resonable volume of incendary filler. There are exceptions of course - whilst tracer and armour piercing incendiary rounds are about the limit of small arms the infantryman generally has recourse to incendiary grenades for his fire starting requirements and a few experimental rounds like Dragon's Breath have been developed.
Some interesting incendiaries:
Game and Story Use
- Kill it with fire
- Even if you don't want to kill it, the ability to start fires can provide a useful distraction, destroy enemy supplies and equipment or create an obstacle on the battlefield.
- Some primitive communities are thought to have driven herds of prey animals off cliffs and into similar death traps by starting brush fires - your PCs may find this useful at some point.
- Before the advent of explosives, incendiaries are your major force multiplier technology.
- Incendiaries - as noted above - can also be extremely effective terror weapons. Even fanatics run when they are on fire1 and the threat of incendiaries - or the sight of them in use on other troops - may be enough to get a formation to break or surrender.
- Most pre-modern incendiaries were extremely dangerous to use. PCs - and game systems - should bear this in mind, but for PCs with suitable mental disadvantages this may not be a problem.