Bradshaw graduated with Bachelor of Science degree on April 20, 1917, shortly following the United States entry into World War I, and was commissioned second lieutenant in the Coast Artillery Corps. He completed his training and embarked for France, where he joined 3rd Anti-Aircraft Battalion during the air defense of Paris. Bradshaw was later transferred to the 2nd Anti-Aircraft Battalion and participated in the Meuse–Argonne offensive in fall 1918.