With the American entry into World War II in December 1941, Dahlquist was sent to England and assigned as deputy chief of staff to Major General Dwight David Eisenhower in early 1942, and, later that year, with the one-star rank of brigadier general, became the assistant division commander (ADC) of the 76th Infantry Division. In June 1943, promoted to the two-star rank of major general, Dahlquist became the first commanding general (CG) of the 70th Infantry Division, becoming one of the youngest division commanders in the U.S. Army. In July 1944, he took command of the 36th Infantry Division, a National Guard formation from Texas that had fought in many difficult battles in the Italian Campaign under Major General Frederick Walker and had recently taken part in Operation Dragoon, the Allied invasion of Southern France.