In 1941, Bolte, by now a lieutenant colonel, journeyed to London as head of a group of army observers and, early in 1942, after the United States had entered World War II due to the Japanese attack on Pearl Harbor followed by the German declaration of war on the United States, assumed the position of chief of staff of U.S. Forces in the United Kingdom, with the one-star general officer rank of brigadier general. With the two-star rank of major general, he returned to the United States in 1943 and raised and commanded the 69th Infantry Division in Mississippi.