In 1940, while fighting the Norwegian Campaign, the Luftwaffe and British air forces carried out the first effective aerial attacks against enemy warships. The British found success first when they sank the light cruiser Königsberg (7.100 tons) on 10 Apr using Blackburn Skua dive-bombers (first success vs. warships larger than a destroyer). The Luftwaffe responded by sinking the HMS Curlew, a light cruiser of 4.200 tons, just weeks later (26 May), using dive-bombing techniques as well (Ju-88s).

During the Dunkirk evacuation, the Luftwaffe sank several British destroyers, but it was not until the raid on Taranto on the night of 10-11 Nov 1940, that for the first time, [British] aircraft were able to heavily damage enemy capital ships: three Italian battleships (plus a heavy cruiser). They did not sink them because they were in shallow waters, but one of battleship was crippled beyond repair.  

The attack was carried out with torpedoes instead of bombs and this proved effective against heavily armored ships. The assault was carried out in a port against static targets, so it remained to be seen if a capital ship could be sent to the bottom in open seas with abundant space to maneuver.

On 10 Jan 1941, HMS Illustrious, a heavily armored aircraft carrier, was attacked by Ju 87B and Ju 87R from I./StG 1 and II./StG 2 (see the photo) south of Malta and heavily damaged despite its strong escort,  its radar that detected the attacking aircraft beyond visual range, its maneuverability, and its fighter CAP (Fulmars).

The Stukas showed that a capital ship could be hit from the air over open seas, but it also proved that heavily armored ships were difficult to sink using bombs only. According to the British damage report, the Illustrious was hit with seven bombs plus a near miss. The carrier remained almost 11 months in repair, but it remained afloat. The next day the Stukas were able to cripple the light cruiser HMS Southampton (9.100 t) so badly that the British scuttled it.

The lessons were learned by the Japanese that included both dive-bombers and torpedo bombers in their attacking formations. They were the first to sink battleships in open seas just eleven months later (the Prince of Wales and Repulse)