A typical Infantry battalion in 1943 was made up of a Headquarters company, a (Heavy) Weapons company and three Rifle companies. Each Rifle company was made up of one Weapons platoon and three Rifle platoons. Each Rifle platoon consisted of three Rifle squads. Each Rifle squad consisted of about 12 to 14 men. A typical battalion consisted of 870 men and the CO had the rank of Major or Lieutenant-Colonel.
Armaments:
The (heavy) Weapons company typically had eight .30 MG's, six 81mm mortars and seven bazooka's. The Weapons platoon had two .30 MG's, one .50 MG, three 60mm mortars and three bazooka's. A Rifle squad had one .30 BAR, one or two .45 SMG's, one M1903A1 rifle with grenade launcher and about ten .30 M1 rifles and or .30M1 Carbines.
Infantry Regiment:
An Infantery Regiment had a Headquarters company, and Anti-Tank company, an Artillery company, a Support and Services company and three Infantry battalions. A Regiments consisted of about 4000men; the CO usually had the rank of (full) Colonel.
Armaments:
The anti-tank company had 9 to 12 x 37mm or 57mm guns, the cannon company had 6 x 105mm guns. Sometimes there were also some 75mm or 105mm pack howitzers.
Infantry Division:
An Infantry Division was made up of three Infantry Regiments, three Medium Artillery Battalions, one Heavy Artillery Battalion, one Engineer Battalion, one Signal Company and a Reccon Troop. A typical Division had about 14.250 men and 2000 vehicles; the CO had the rank of General.
Armaments:
Apart from the Regimental Artillery each of the three Medium Artillery Battalions had 36 x 105mm guns. The Heavy Artillery Battalion had 12 x 155mm guns. The Engineer Company had a minimum of 24 flamethrowers. The Reccon Troop had a number of jeeps and small armoured vehicles, along with some MG' and a 81mm mortar.
Except from these standard units the Division sometimes also had a number of independent units directly attached to the Division itself, like Mechanised Cavalry groups or squadrons, and Artillery, Anti-Aircraft, Tank, Tank Destroyer and Military Police Battalions.These were attached to divisions as needed. In the ETO these attachments were very common and alsmost permanent.
Ofcourse are all the numbers mentioned above only a theorytical situation, and the reality could be very different, depending on the situation.