He graduated from Shortridge High School in Indianapolis in 1931 and attended Wabash College in Crawfordsville for two years.

He graduated from the United States Military Academy in 1937 and was commissioned a second lieutenant in the Coast Artillery Corps.

After serving as operations and training officer of the Harbor Defenses of Narragansett Bay, Fort Adams, Rhode Island, General Underwood was selected to attend the Task Force Staff Officers' Course conducted by the Operations Division of the War Department General Staff.

Upon his return from China in May 1947, he was assigned to the Plans and Operations Division, War Department General Staff.

General Underwood received the Distinguished Service Medal, the Legion of Merit with 2 Oak Leaf Clusters, the Army Commendation Ribbon with One Oak Leaf Cluster, and the Special Breast Order of Yun Hui (Chinese).