He attended the United States Military Academy at West Point, where he was a classmate of future Chief of Cavalry Herbert Ball Crosby, and graduated in 1893.

He taught mathematics at West Point from 1895 until 1898, when he took part in the Santiago Campaign of the Spanish–American War, after which returned to teaching from 1898 to 1899.

The citation for his Army DSM reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Brigadier General William Mackey Cruikshank, United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility during World War I.

Subsequently, during the advance on 18 July, due to his tactical knowledge and successful placing of the guns, he greatly assisted in the repulse of the enemy.

Later he rendered valuable services as Commander of Artillery of the 4th Army Corps.After his return to the United States, he served on the General Staff Corps from 1920 to 1924.