A force of 44 Fleet Air Arm aircraft attacked a U-boat base 5 mi (8.0 km) south of the town and port of Harstad.

The attack was carried out by the First Cruiser Squadron under the command of Vice Admiral Rhoderick McGrigor, second-in-command of the Home Fleet, in his flagship HMS Norfolk.

The Avengers would then arrive, each armed with four 500 lb (230 kg) bombs and carry out glide-bombing runs in quick succession, 846 Squadron attacking Black Watch and 853 Senja.

[6] In Kilbotn village, 1 mi (1.6 km) from the main target Black Watch, one bomb fell near some houses after a fault in the launching mechanism of one of the Avengers.

[8][9] The First Cruiser Squadron sailed south to provide air-cover for Operation Cleaver, the passage of ships in the Skagerrak and arrived back at Scapa Flow on 10 May.

Captain Lange reported in 2008 that Germany's leader Dönitz had ordered the immediate cessation of all U-boat attacks on Allied shipping as part of the surrender of naval forces on 4/5 May.

Lange stated that this signal had been received on board U-711 in the early afternoon and therefore his crew believed their war was over before the Fleet Air Arm attack arrived.

Of the four British aircrew lost in Operation Judgement, Lt. Hugh Morrison from Wairarapa, New Zealand, Senior Pilot of 882 Squadron, is buried in Narvik New Cemetery.

[10] Decorations to personnel taking part in Operation Judgement were awarded in the King's Birthday Honours of June 14 and listed in the London Gazette.

[14][15] In June 2013 people from Kilbotn and Harstad fixed a board on the hillside at Barnvika, as close as possible to the Black Watch anchorage, giving details of the action.