Promoted to Lieutenant (junior grade) on 15 June 1942, he was killed on 26 October 1942 when Porter was torpedoed by an Imperial Japanese Navy submarine during the Battle of the Santa Cruz Islands.

She was laid down by Brown Shipbuilding Co., Houston, Texas, 4 August 1943; launched 10 October 1943; sponsored by Mrs. Alfred Janssen, stepmother of Lieutenant (j.g.)

In the months that followed, Janssen and her sister ships attacked numerous submarine contacts while cruising between the United States and the Azores; and, after a brief rest in North African ports, they returned to Norfolk, Virginia, 2 May.

Janssen arrived New York 24 September 1944 for training exercises, and in December took part in an emergency patrol off the coast of Maine, where increased U-boat activity was anticipated.

Too late to take active part in the war against Japan, the ship embarked 100 returning veterans at Pearl Harbor and brought them to San Pedro, Los Angeles, 9 September.

Janssen received one battle star for World War II service and shared in the Presidential Unit Citation awarded to the various ships of the Bogue task groups for outstanding antisubmarine work in the Atlantic during 1943–44.