They were also operational during the Battle of Britain Britain that autumn, but it was the land-based Supermarine Spitfires and Hawker Hurricanes and their pilots that provided the principal aerial defense for the UK. Sea Gladiators also assisted during the defense of Malta, where one shot down an Italian bomber. Gladiators were removed from front-line service around Britain by 1941. The more modern, monoplane Blackburn Roc was able to shoot down a Junkers Ju 88 fighter-bomber attacking a convoy in 1940. However, the Roc was no match for German Messerschmitt Bf 109 or Focke-Wulf Fw 190 fighters and could not even perform as well as Britain's own Blackburn Skua. Considered one of the worst fighters of the war, the Roc was, by late 1940, taken out of front line service and consigned to training, target towing, and rescue duties. A more modern monoplane fighter, the Fairey Fulmar, was introduced in 1940 to replace the obsolete Sea Gladiator. It was a two-seat design and was large and less nimble than the Axis fighters it opposed. Nonetheless, while protecting convoys to Malta, Gladiators shot down ten Italian bombers and six Axis fighters. During the war, they provided air cover for the raids on Taranto and Petsamo, protected convoys to Russia, and supported invasions of North Africa and Italy. Fulmars shadowed the German battleship Bismarck enabling Fairey Swordfish torpedo bombers to catch up with her. The UK upgraded their naval fighter squadrons in 1941 by adapting the highly successful, land-based Hawker Hurricane to carrier use. The Hawker Sea Hurricane performed well while protecting the Malta convoys and, operating from escort carriers, many Atlantic convoys.