Immediately post-WWII and before and during the Korean War, US Army infantry units underwent several major changes, with several new or relatively new weapons and technologies being introduced;

• M18 57 mm recoilless rifle

• M20 75 mm recoilless rifle

• M27 105 mm recoilless rifle

• M20 3.5 inch "Super Bazooka"

• M26 Pershing/M46 Patton

• M4A3(76)W HVSS Sherman

• Helicopter

Now, a list of major changes;

• In June 1945, an assault section with 2.36 inch rocket launchers and a special weapons section with 57 mm recoilless rifles was added to the weapons platoon of the rifle company, increasing the company's strength from 193 to 242 men

• Prior to the Korean War, the rifle squad was reduced from twelve to nine men

The BAR ammunition bearer and two scouts were eliminated. The rifle squad now consisted of a leader, his assistant, a two-man BAR team, and five riflemen, one of them armed with the sniper version of the M1 rifle (previously, there had only been authorized one sniper per platoon, to be given to a select rifle squad)

• With the reduction in rifle strength, a fourth, 9-man "weapons" squad was added to the rifle platoon

The weapons squad was armed with 2.36-inch rocket launchers and .30 caliber light machine guns. The 60 mm mortars and 57 mm recoilless rifles (a weapon introduced very late in WWII) stayed in the company's weapons platoon.

• In June 1945, a platoon of 75 mm recoilless rifles was added to the heavy weapons company

• In 1947, one of the two machine gun platoons in the infantry heavy weapons company was deleted and the number of 81 mm mortars and 75 mm recoilless rifles were each reduced from six to four. Six 3.5 inch "Super Bazookas" replaced the previously used nine 2.36 inch rocket launchers in this company. During the Korean War itself, the 75 mm rifles were replaced with 105 mm weapons.

• M20 3.5 inch "Super Bazookas" eventually replaced the less-powerful 2.36 inch rocket launchers at all levels; three Super Bazookas were given to each rifle platoon headquarters during the Korean War

• In June 1945, The cannon companies of the infantry regiments replaced their towed 105 mm howitzers with 105 mm howitzer-armed Sherman tanks, and the antitank companies gave up their towed 57 mm guns for 90 mm-armed tanks

• Prior to the Korean War, the cannon and antitank companies were completely eliminated from the infantry regiments, and heavy mortar company of 4.2 inch mortars and a company of 22 tanks became organic to each regiment.

• In 1952, a helicopter and a fixed-wing airplane were placed in a new "light aviation section" in each infantry regiment

• In 1947-1948, a tank battalion was made a permanent part of each infantry division. During WWII, tank battalions were only temporarily "attached" to divisions and could be moved around at will

The tank battalions and companies were armed exclusively with, or a mix of, M26 Pershing and M4A3(76)W HVSS tanks. The now-standardized and more common M4A3 Sherman proved more reliable in Korea than the M26 Pershing, so the Pershings were withdrawn and replaced with the M46 Patton, an improved M26 with a more powerful engine and transmission.

Source:

CMH 60-3: Infantry, Part I: Regular Army (World War II to Korea), by John K. Mahon and Romana Danysh

CMH 60-3: Infantry, Part I: Regular Army (The Korean War), by John K. Mahon and Romana Danysh