The American Soldier, 1938

World War I, after an initial period of mobility, soon settled down to a stalemate, costly in lives and equipment. The warring powers in western Europe faced each other across trenches in stabilized defensive lines. It was a war of artillerymen and infantrymen, neither of whom was able to force a decision. To help break this stalemate the British developed a secret weapon, an armored fighting vehicle, the tank. Tanks were fiat used by the British in World War I in September 1916. Both sides recognized the impetus given to the attack by the use of tanks, and the Allies and the Germans had employed them in 91 engagements by the end of World War I.

Development of both armored tactics and materiel marked the period between the two world wars. After a short-lived experiment aimed at establishing a mobile mechanized force at Fort Eustis in 1931, the Cavalry took over the role of developing such a force at Fort Knox, Kentucky, in 1933. In early 1938 two cavalry regiments, the 1st and the 13th, and other Fort Knox units were used to form the 7th Cavalry Brigade, with the then Brigadier General Daniel Van Voorhis in command. Later that year he was succeeded by Col. Adna R. Chaffee, a brigadier general by November 1938.

In the right foreground is Brigadier General Adna R. Chaffee. Known as the "Father of the Armored Force," he dedicated his career to the development of armor. General Chaffee is wearing the summer khaki service shirt, with the silver metal star insignia of his rank on the shoulders/rap, and a black four-in-hand cravat. His ribbons are for the Distinguished Service Medal, the Cuban Pacification Medal, and the World War I Victory Medal. His undress riding boots are of cordovan leather, and his pistol belt, magazine pockets, and fiat aid pouch are ribbed, woven, olive drab web. He wean the standard khaki field cap authorized only for personnel of the Air Corps and for tank or mechanized units from 1933 to 1939. The patch on the field cap bearing the insignia of rank was distinctive to armored organizations. In General Chaffee's case, it is black velvet, denoting a general officer. Other officers wore a patch the color of their basic arm, yellow for cavalry, scarlet for artillery, or light blue for infantry. In the left foreground is a sergeant, also in the khaki summer service uniform, with the insignia of grade on his shirt sleeves, three olive drab chevrons. He wean a tanker's helmet, the regulation laced field boots, and laced breeches. In the background are officers and enlisted men and vehicles of the Cavalry Brigade.