None of the 10 shells fired at Port Gregory caused any damage, and the attack was not noticed by the Allied naval authorities until a radio signal sent by Tosu was intercepted and decoded a week later.

[2] In early 1943, the major Japanese headquarters directed their forces to make small attacks on Allied positions, in an attempt to divert attention away from the planned evacuation of Guadalcanal, Operation Ke.

From a range of 7,000 metres (7,700 yd; 4.3 mi), her crew fired about 10 rounds from the submarine's 100 mm (3.9-inch) Type 88 deck gun, at a derelict crayfish cannery, which they had misidentified as an ammunition factory.

[5] Allied naval authorities only learned of the attack when the submarine's battle report radio signal was intercepted and decoded a week later.

Within Allied naval circles, it was regarded as a "graphic example of the poor planning and inadequate doctrine so common in the Japanese submarine force".