[T]he long poles dropped, presenting a row of knife-edged blades four deep.
— S M Stirling, A Meeting at Corvallis
A bill is a polearm, consisting of a simple blade with a long handle, and as a weapon can be fairly versatile. The bill's main advantage over weapons is that it can be used in a great variety of ways - it can stab, as much as it can bludgeon or smash, with equal effect.
Compared to normal pikemen, these units don't seem to be that interesting, apart from the fact that they deal brutal amounts of splash damage. Worse of all, they also lack the same range as normal pikemen do. So, what is the big draw on these guys, you might wonder? well, there are two reasons.
First of all is the fact that these fellows don't really need Centralisation. As a result, while other factions such as Burgundy, Hungary, Portugal, Spain, the Empire and Sicily will be fumbling around for shiny new pikes to replace their outdated Spear Sergeants, you will have managed to obtain Billmen to do your bidding. This means that you will tend to have a better advantage in anti-cavalry melee infantry much faster in the pre-Centralisation late game before most other factions, until they can finally get the longer range of pikes on their side. Statistics-wise, Billmen and Pikemen have more or less the same amount of stats except for the Billman's lack of range, traded off for splash attack. Together when amassed, bill formations are essentially massive walking blenders into which any melee unit that gets sucked in will be neatly minced up into hamburger. Pikemen may be able to strike first in most melee encounters, but it's the Billmen who will always have the final say.
So in general, Billmen are meant to succeed at one thing, and that is as a potent anti-melee force. In the pre-Centralisation part of the game, your billmen can be used as an effective cavalry screen. if an enemy brings out Arbalests and Pikemen, you however should switch your tactics, and use your Billmen in a more offensive manner, marching them to crash into the enemy, where their outranged albeit powerful attack can be brought to bear on the foe. Keeping them standing in rank before your enemy would be worthless, as they can then be easily cut down by the archers and pikes of your foes, in which case only offensive tactics accompanied by cavalry could actually help secure victory for your forces - cut your enemy down before he can stab you!
- Early Supremacy — As billmen can be obtained in the pre-Centralisation late game, they are a great boost for those capable of recruiting them, although they will soon be outranged by the costlier but more efficient Pikemen.
- Planning for Obsolescence — Once Centralisation is achieved, Billmen become weaker as a defensive force. This means you should use offensive tactics accompanied by cavalry — cut your enemy down before he can stab you!
The bill was based off the bill hook, an agricultural tool that consisted of a long vertical blade and a long wooden handle. Unlike a scythe which had its blade positioned at a quadrangular angle, a bill had its blade positioned at an angle perpendicular to the handle, making it a robust and fairly efficient type of polearm. Bills were popular in the Mediaeval Era, because they could be quickly fashioned from existing agricultural tools, and when used offensively, proved to be devastating as an anti-cavalry weapon. Although the Bill was usually associated with England in the Middle Ages, bills were also used by Indian and Italian armies, and in non-professional armies of the same period.