Eugene Santschi Jr. was born in Alton, Illinois, on January 15, 1883 to Swiss immigrants Eugene Sr. and Emma Chausse. At some point in his youth, his family moved to the coal-mining region of Utah. Thereafter, according to a Utah Since Statehood biographical sketch of Santschi, he enlisted in the United States Army and spent two years overseas on active duty, and he was involved in both the Philippine Insurrection (1899-1902) and the Boxer Rebellion in China (1900-1901). In 1903 Santschi returned to the United States and enrolled in the United States Military Academy at West Point, New York, and graduated with the class of 1907. From 1907 to 1914, Santschi was stationed at Fort Douglas, Utah. In 1908 Santschi attended the Agricultural College of Utah (now Utah State University) at Logan, Utah and received a BS that year. Although Santschi was stationed at Fort Douglas during this time period, the military sent him on numerous trips to Japan, the Philippines, and China, where he spent time studying military tactics and touring the battlefields of the Russo-Japanese War of 1905. While in the United States, Santschi met and married Amanda Marie Holmgren of Logan, Utah on June 5, 1911.

From 1914 to 1917, Santschi lived in Logan, Utah to serve as a ROTC instructor at the Agricultural College of Utah. With the war in Europe taking place, Santschi was recalled to the Tactical Department at West Point, where he remained until 1919. In 1919 Santschi went to Europe and served in the army of occupation in Germany as chief of saff of the 2nd Brigade, until 1922.

Thereafter, Santschi's career allowed him to serve in many positions and his military rank progressively advanced. From 1922-1923, Santschi served at the Command and Staff School, Ft. Leavenworth. From 1923-1927, he was an instructor at the Command and General Staff School. During 1927-1928 he worked at the Army War College, from 1928-1929 at the Naval War College, and from 1929—1932 in the Organized Reserves, 6th Corps Area. During 1932-1936 he was an instructor at the Naval War College and from 1936-1938 he was in command of the 34th Infantry at Ft. Meade. From 1938-1940, he served as chief of staff of the Hawaiian Division, and from 1940-1941 he was in command of the 1st Infantry, Ft. Warren, Wyoming. In 1943 Santschi retired from the military, but because of World War II, he was recalled to active duty until 1946. In 1945 he was awarded a Legion of Merit and the Order of the British Empire. After the war, Santschi officially retired and moved to California where he died on January 19, 1959 in Palo Alto.