[5] During World War I, Merle-Smith served in the United States Army's 165th Infantry Regiment, 42nd Division, achieving the rank of captain.
[6] Captain Merle-Smith was awarded the Distinguished Service Cross for his actions on July 28, 1918, with the medal's citation reading as follows: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Distinguished Service Cross to Captain (Infantry) Van Santvoord Merle-Smith, United States Army, for extraordinary heroism in action while serving with 165th Infantry Regiment, 42d Division, A.E.F., near Villers-sur-Fere, France, on 28 July 1918.
[10] Merle-Smith returned to the army with the outbreak of World War II,[11] achieving the rank of colonel.
[5] In 1943, Colonel Merle-Smith suffered a mental breakdown brought on by heavy staff work in the South Pacific.
[13] The couple would eventually have four children: Three months after his breakdown, Merle-Smith died in Cove Neck, New York, on November 9, 1943.