Following graduation from Brown, he enlisted in the United States Navy in July 1940 and was commissioned as ensign in the Naval Reserve on January 30, 1941.

While Bates was stationed there, his father was killed in a plane crash at the Washington National Airport on November 1, 1949.

Bates resigned his reserve commission — he had attained the rank of lieutenant commander by that time — on February 14, 1950, to fill the seat of his late father in the United States House of Representatives.

For nearly two decades, until his death in 1969, Bates staunchly advocated a strong military posture for the United States.

The Bates Bridge, which crosses the Merrimack River between Groveland and Haverhill, Massachusetts, is named in his honor.