[b]Early 20th Century Organizations [/b]

World War I witnesses a change in the organization as the Machine gun enters its infancy. Infantry Regiments receive Machinegun Battalions and companies. Entire companies devoted to nothing but Machine guns. By the end of WWI, each Battalion has a Machine gun Company. A standard Infantry Regiment would look like this:

[u][b]Infantry Regiment[/b][/u]
		Regimental Headquarters Company
	1st Battalion Headquarters Company
		A Company (Line)
		B Company (Line)
		C Company (Line)
		D Company (Machine gun)
	2nd Battalion Headquarters Company
		E Company (Line)
		F Company (Line)
		G Company (Line)
		H Company (MG)
	3rd Battalion Headquarters Company
		I Company (Line)
		K Company (Line)
		L Company (Line)
		M Company (MG)

With the introduction of the Machine gun company to the Infantry Battalion, the High Impact Ranged weapon we used to see as a distinct corps 200 years prior is now at the Battalion Level. 

WWI also saw the introduction of the Tank and the Airplane. To counter both of these the Anti-Tank weapon (AT) and the Anti-Aircraft weapon (AA) were created. The years between the two world wars introduced the Anti-Aircraft Battalions which were included at the Division level and Anti-Tank platoons which were included at the Battalion Level. Scouts and Recon units were also added to the Infantry Battalion. Previously the job of scouting the enemy was performed by Infantrymen. They still are today, but there are also units specifically designed for this purpose.

By 1940, a US Infantry Battalion now consisted of the following:

Battalion Headquarters Company
3x Line Company (A-C for 1st Bn, E-G for 2nd Bn & I-L for 3rd Bn.)
1x Weapons Company

The weapons Company had the Intelligence & Reconnaissance Platoon (I&R) which conducted reconnaissance in front of the Battalion. They may also perform surveillance missions. The Mortar Platoon; generally used the 81mm mortar at Battalion level and 4.2" at Regimental level. The AT platoon was equipped with 57mm AT guns initially and were eventually replaced with the improved 75mm AT gun as enemy Armor improved.

The combined Arms integration of Machine guns, Anti-Tank guns, Mortars and Infantry is now down to the Battalion level. In fact, a standard Line Company now has a weapons Platoon consisting of a section of 60mm Mortars and six .30 caliber MGs. Eventually, company would replace their 60mm Mortars with 81mm and Battalion would replace their 81mm mortars with 4.2" mortars.

The Rifle Squad in World War II consisted of 10 men just as it did in Genghis Khan's Army centuries earlier. Everyone carried the M1 Garand Rifle except the BAR gunner; he carried the Browning Automatic Rifle (BAR). The BAR was no machinegun as it had a limited magazine capacity, but it was full automatic and used a high velocity round. This the beginning of placing the High Impact Ranged weapon at Squad level. The Assistant Squad Leader in a Rifle Squad in WWII also had a grenade projector. He carried the M1903A3 Bolt Action rifle and using a blank cartridge with the grenade projector in order to send a hand grenade flying about 200 yards.

During WWII, German units formed Kampfgruppen or Battle Groups. These battle groups were a Combined Arms unit at the Brigade level (sub-Divisional). Generally they were composed of two battalions of Panzergrenadieren (Mechanized Infantry), a battalion of Panzers (Armor) a Company of Pioneers (Combat Engineers) and a Battalion of Field Artillery. Just as the British, Prussians and Austrians learned from Napoleon 140 years earlier, the Americans, British and Russians learned from the Germans. During the rest of WWII and the Korean War they established combined Arms Teams and Task Forces, but didn't make it permanent until the late 1950's.