New Made Item: Quality 3' x 5' flag. Ready to display. Complete with 2 hang side brass grommets. Recommended for indoor use; synthetic.

With the attack on Pearl Harbor on 7 December 1941, the "great laboratory" phase for developing and testing organizations, about which Marshall wrote in the summer of 1941, closed, but the War Department still had not developed ideal infantry, cavalry, armored, and motorized divisions. In 1942 it again revised the divisions based on experiences gained during the great GHQ maneuvers of the previous year. As in the past, the reorganizations ranged from minor adjustments to wholesale changes.

1st Cavalry Division retained its square configuration after the 1941 maneuvers, but with modifications. The division lost its antitank troop, the brigades their weapons troops, and the regiments their machine gun and special weapons troops. These changes brought no decrease in divisional firepower, but placed most weapons within the cavalry troops. The number of .50-caliber machine guns was increased almost threefold. In the reconnaissance squadron, the motorcycle and armored car troops were eliminated, leaving the squadron with one support troop and three reconnaissance troops equipped with light tanks. These changes increased the division from 11,676 to 12,112 officers and enlisted men.

The last of the 1st Cavalry Division's mounted units permanently retired their horses and converted to infantry formations on 28 February 1943. However, a mounted special ceremonial unit known as the Horse Platoon – later, the Horse Cavalry Detachment – was established within the division in January 1972. Its ongoing purpose is to represent the traditions and heritage of the American horse cavalry at military ceremonies and public events.