Cusic, Arthur John, MoMM1c

                                      Porpise-class Submarine

First and second war patrols, December 1941 – July 1942

Plunger's second war patrol, 5 June to 15 July, took her off Shanghai. On this patrol, she sank the 4,700-ton cargo ship Ukai Maru No. 5 on 30 June and Unyo Maru No. 3 on 2 July before returning to Midway 15 June.
 

While on this patrol, White nearly sank a ship by accident that would have caused an international uproar. Through diplomatic channels, President Roosevelt had arranged an exchange of political prisoners trapped in the United States and Japan by the outbreak of war, including U.S. Ambassador to Japan Joseph C. Grew. They were put aboard the neutral vessels Asama Maru and S.S. Conte Verde for transfer from Japan to the United States. They were to sail with lights and other markings on a prearranged route, as would the vessels returning the Japanese.

On 5 June, [COMSUBPAC] English had sent instructions to his submarines, describing these ships, the routes, and the markings. Later, on 25 June, when the vessels actually got under way, English sent further messages, designed to assure immunity from submarine attack. Dave White failed to receive these messages. In the early morning hours of 30 June, he picked up Conte Verde and began an approach, somewhat astonished to find a ship all lighted up.
....

On Plunger, White had Conte Verde fixed in his periscope hairs and the crew at battle stations when his communications officer, having picked up and just decoded this fifth immunity message, rushed up into the conning tower. White broke off the attack at the last minute, settling for a photograph taken through the periscope from a range of 800 yards.

Third and fourth war patrols, October 1942 – January 1943

In October, as U.S. forces pushed on to Matanikau and Cape Esperance, Plunger departed Pearl Harbor on 12 October to reconnoiter the area and to block the "Tokyo Express." However, Plunger hit an uncharted reef 2 November, destroying her sound gear and damaging her bottom.

After repairing at Brisbane, Plunger returned to the Guadalcanal area for her fourth war patrol and operated off Munda, where Japanese barges were coming in at night, unloading troops and supplies, and departing by daybreak. On the night of 16 – 17 December she slipped past four destroyers and attacked two others unloading at Munda Bar. After seeing two of her "fish" explode, she slipped away from a counterattack. After another attack with unknown results the next night, and a bomber attack while heading home 8 January 1943, she arrived Pearl Harbor 12 January.
 

1943

Plunger continued reconnaissance patrols throughout the spring and summer. She sank Taihosan Maru 12 March, and Tatsutake Maru and Kinai Maru 10 May. In June, she joined Lapon (SS-260) and Permit (SS-178) in the first U.S. penetration into the Sea of Japan, an area abounding with Japanese shipping. Crossing the southern end of the Sea of Okhotsk, the ships returned to Midway 26 July but departed again 6 August to return to the Sea of Okhotsk. Plunger sank 3,404-ton Seitai Maru there 20 August and 4,655-tonRyokai Maru 22 August. Returning to Pearl Harbor 5 September, the ships were the only U.S. vessels to complete two patrols to this area until the final weeks of the war.

In October, Plunger reconnoitered in the Marshalls area. She added lifeguard duties to her resume as U.S. bombers hit the islands, picking up a downed aviator 15 November. During the rescue, a Zero strafed the boat, seriously wounding the executive officer and five bluejackets. Nevertheless, the submarine rescued Lt. (j.g.) Franklin G. Schramm.

1944–1945

Frequent depth charge attacks pursued Plunger in January 1944 as she patrolled off the Japanese main islands. The risk was profitable, however, as she sank Toyo Maru No. 5and Toyo Maru No. 8 on 2 February and Kimishima Maru on 23 February. Returning to Pearl Harbor 8 March, Plunger departed again 8 May to patrol the Bonin Islands. In July, she patrolled in and around Truk.

On 19 September 1944 she reported to Pearl Harbor for overhaul. She departed 15 February 1945 for New London, to serve in a training capacity until 25 October, when she reported to New Haven for Navy Day celebrations. On 30 October she reported to the Boston Navy Yard, where she decommissioned 15 November 1945.