The make-up of an army

I have always been at a loss when books talk about divisions and battalions, even about armies. I get to the point where I’m not sure just what an army is. So here’s the results of my research.

A field army consists of a number of corps which are in turn divided into divisions. A division has all the combat and support units to operate independently. They are in turn divided into brigades or regiments. Regiments are divided into battalions (just to confuse us, some countries call their battalions regiments). It is at the battalion level that different types of combat and support troops, for example infantry, artillery and sapper units first combine. Battalions are, in turn, divided into companies, then we have platoons and finally, squads. To go back to the top of the hierarchy, a number of field armies may be combined to form an army group.