While researching my grandfather's military background, I have noticed something. Most divisions, when all of the various units are listed, they all seem to have numerical designations. For instance: 505th PIR, 82nd Airborne Division. But, every time military police is listed, it just says "military police platoon." Did the MP platoons not have a numerical designation? As far as insignia, would they have the crossed pistol tab on their lapel instead of the crossed rifles of the infantry, and the divisions patch on the shoulder?
No, US divisional / regimental MP units do not have a seperate designation. They are part of the division or regiment's Headquarters Company. As for insignia, you are essentially correct. They would also normally have the MP brassard (that big black arm band with MP on it) when on duty.
In the pre-WWII days of the 'square division' (4 regiments) each division had a numbered Military Police Company. For example, 34th MP Co in the 34th Inf Div. When divisions went 'triangular' at the beginning of the war, auxiliary units were generally diminished. The Military Police Company became a Platoon, not officially numbered. But it was still COMMONLY referred to as the n-th MP Platoon. It was simply the perpetuation of a habit, and avoided the need to recite the organizational chain Where the MP units were placed within the division seems to have varied. I suspect that they were most often under command of Division Train or Division Special Troops. I'm not aware of the MPs ever being considered part of the Headquarters Company, but rather alongside and partner with them, just as was, for example, the Signal Company. Their most common duties were command post security, traffic management, and prisoner control. And in a pinch anyone not on the line hauled ammunition and served as litter bearers when needed.
