Bjornstad received his commission as first lieutenant in the 13th Minnesota Infantry on May 7, 1898. On August 17, 1899, he was a captain of the 42d United States Volunteer Infantry and a first lieutenant, 29th Infantry, by February 1901. He was engaged in thirty-four actions and battles in the
Philippines between 1898 and 1904. In 1909, he was an honor graduate of the Army School of the Line, and in 1910 he graduated from the Army Staff College. Bjornstad performed General Staff duty from 1911 and 1912, and from 1912 to 1913 he was the United States
military attaché in Berlin. He then was an instructor at the Army Staff College in 1915 and 1916. In late 1916, he was the professor of military science and tactics at
Harvard University. After this he returned to the General Staff. He became a brigadier general on July 12, 1918, with a date of rank from January 26, 1918. Bjornstad then became the chief of staff, Third Corps, followed by duty as commanding general, 13th Infantry Brigade in 1918 and 1919. He participated in all the major engagements in France. During 1919 he was on duty at the General Staff college, and from 1920 to 1923, he commanded Fort Snelling, Minnesota. Bjornstad belonged to the Masons, and retired in 1928. == Awards ==