In June 1944, "Bangor" was involved in Operation Neptune - the naval component of the D-Day landings in Normandy. The 9th Flotilla was part of Force J, sweeping channels. In the post assault phase the Flotilla was part of Task Force 129, which sailed from Portland on the night 24/25 June with the intention of bombarding Cherbourg. At 11:55 the minesweepers of Unit 1 (the 9th MSF) made their turn to sweep Fire Support Area 3, closely followed by the bombarding ships of group 1. As they entered the area they came under heavy fire; the German batteries had evidently been waiting until they were well within range. The destroyers, screening on the flanks, made smoke, but the enemy fire increased and after sweeping just three miles (half the intended distance) the minesweepers was forced to withdraw northwards.