Here are some words you might find in the books, with a brief layman’s explanation to their meaning:

Spanish sympathiser for French cause

Firing step behind parapet

Battalion                    The unit of a regiment in active service. Usually another battalion would be at the regiment’s home base. Some regiments raised several battalions.

Group of cannon, usually six or eight

Accommodation indoors

Soldier’s camp in the field - outside        

A group of battalions, typically three in the British army

Nickname for standard British musket

Ammunition wagon