Battle (formation)

A battle or battaile was a medieval military formation, analogous and ancestral to the modern term battalion. In late medieval warfare, field armies were often drawn up into three main battles, also called guards: the vanguard, the middle guard, and the rearguard, often abbreviated to simply the van, middle, and rear. These terms imply, correctly, that the van preceded the middle, which in turn preceded the rear, into battle if the battles were arranged sequentially as a column. If arranged abreast, the van was on the right and the rear the left.

...
Wikipedia