In April 1941, Geiger made his way from Lisbon to Gibraltar, where he changed from civilian clothes to his military uniform. He had lunch with the governor at Government House, in a visit which lifted British morale in Gibraltar. He was on his way to the Western Desert, as the first U.S. military observer attached to the British 8th Army. In August, he became commanding general, 1st Marine Aircraft Wing, Fleet Marine Force, in which capacity he was found upon the United States' entry into World War II.