Regiment

[Mobhack]

Also remember that cavalry is different (naturally!).

Commonwealth cavalry units of batallion size are called "Regiments" - and unlike the infantry, were not expanded in wartime.

The Royal Tank Regiment is an exception, not classified as cavalry, and formed of several regiments (1/RTR, 2/RTR etc).

The artillery is a Regiment which contains regiments, a batallion sized group of 3-4 batteries being termed a regiment as with the cavalry.