[2] He began attendance as a member of the class of 1918, which graduated in August 1917 because of the demand for trained officers as the United States Army expanded in anticipation of U.S. entry into World War I.

[3] From July to October 1919, Hasbrouck was assigned as adjutant of Base Section Number 2, a Services of Supply facility in Bordeaux.

[3] From October to December 1919, Hasbrouck served in Warsaw as part of the American Relief Administration, where he instructed the Polish army on the employment of mechanized military equipment.

[3] In January 1920, Hasbrouck joined Motor Command Number 34, a unit of 2nd Brigade, American Forces in Germany.

[3] Hasbrouck subsequently served as an instructor assigned to the Army's Motor Transportation Corps School in Kruft.

[3][5] In November 1920, Hasbrouck returned to the United States and was assigned to the 76th Field Artillery Regiment at Camp Pike, Arkansas.

[1] In 1936, Hasbrouck was promoted to major[5] and began attendance at the United States Army War College, from which he graduated in 1937.

[5] He remained in command until February 1942, when he was promoted to colonel[5] and assigned as chief of staff for the 1st Armored Division at Fort Knox.

[1] He served with the 1st AD in England as it completed final preparation to enter combat, then returned to the United States in August.

[1] In August 1943, Hasbrouck was assigned as deputy chief of staff for Twelfth United States Army Group, the headquarters that controlled most U.S. forces in Europe.

[1][6][7] After retiring from the Army, Hasbrouck resided in Washington, D.C. and was the military advisor for the Hoover Commission, which studied the organization of the federal government and made recommendations for improvement and modernization.

[7] In addition, he provided assistance to historians, researchers, and writers who studied the 7th Armored Division's wartime service.