Okay here is how I understand most of the US Military's unit tree. Assume we're talking about an infantry units, no vehicles. 8 to 12 men = Squad 4 Squads = Platoon 4 to 5 Platoons = Company 3 to 5 Companies = Battalion 3 Battalions = Brigade 2 or 3 Brigades = Division So where do Regiments come in? Are they roughly equal to Brigades? Or are Regiments only used with certain types of units (aviation or armored)?