'Proteus' was a British operation in support of 'Fortitude' in the form of an armed reconnaissance in force to suggest that the British were assessing the feasibility of a seaborne assault on Narvik on the north-west coast of German-occupied Norway (16/18 May 1944).

The operation was attempted immediately after 'Brawn' by the same forces. Under the command of Vice Admiral Sir Henry Moore, second in command of Admiral Sir Bruce Fraser’s Home Fleet, this Force 7 comprised the fleet carrier Victorious, heavy cruisers Devonshire and Kent, and destroyers Marne, Matchless, Milne, Musketeer, Oribi, Savage and Venus. The force departed Scapa Flow in the Orkney islands group on 12 May and steamed toward the Norwegian coast to reach its designated flying-off position during the afternoon on 14 May.

It was clear by this stage of the undertaking that the weather was unsuitable for flying, and the force stood off to the north-west until the following day. Even though conditions were far from suitable during the afternoon of 15 May, the attacking force was launched in the hope of an improvement over the target. Unfortunately the target area was covered by a thick bank of cloud with no apparent opening and the strike had no option but to return, landing without incident.

With the tactical advantage of surprise now lost, Moore decided to abandon 'Brawn' and head south to undertake 'Proteus' on the following day. By 09.00 on 16 May the weather conditions had deteriorated to the point that flying operations were not feasible, and Moore decided to withdraw Force 7 to the north-west. A weather reconnaissance was flown by two Fairey Barracuda aircraft from Victorious in an effort to locate a break in the weather so that 'Proteus' could be attempted. One Barracuda returned and reported adverse weather for at least 120 miles (195 km) to the south-west, and the other Barracuda missed the carrier and was lost.

Moore then abandoned 'Proteus' and ordered his ships back to Scapa Flow, which they reached during the afternoon of 18 May.