[2] Between the wars, he served aboard the transport America in the Asiatic Station, the battleship Florida, the destroyer Hopkins, the fleet replenishment oiler Ramapo, and the heavy cruiser Indianapolis.

[1][3] He went to sea as commanding officer of the light cruiser Cleveland from August 14, 1944 to early 1945, participating in the capture of Peleliu, Anguar, and Ngesebus; and the recapture of Corregidor and Mariveles.

He served successively as assistant chief of naval personnel; as assistant chief of naval operations; as budget director of the Navy from 1946 to 1950, in which role he played a minor part in the Revolt of the Admirals when his testimony before a Congressional committee suggested that Secretary of Defense Louis Johnson had usurped the powers of Congress by unilaterally refusing to spend appropriated funds;[5] and as deputy comptroller of the Navy Department from 1950 to 1952.

On August 23, the Second Taiwan Strait Crisis erupted when People's Liberation Army forces began shelling Republic of China positions on the disputed islands of Quemoy and Matsu.

Hopwood deployed the Seventh Fleet into the Taiwan Strait to help the Nationalist government protect Quemoy's supply lines, as directed by Admiral Harry D. Felt, Commander in Chief, Pacific (CINCPAC).