During World War I, Magruder served with the 112th Field Artillery within the American Expeditionary Forces in France.

He served in this capacity until 1924, when he was assigned for study at Command and General Staff College at Fort Leavenworth, Kansas.

During World War II Magruder served in the Office of Strategic Services (OSS), as deputy director under the leadership of General William J. Donovan.

Core elements of it, however, were maintained in the new Strategic Services Unit (SSU), located in the then Department of War.

This biographical article related to World War II United States Army personnel is a stub.