Sperrle's first task against the British Isles was during the Kanalkampf (Channel Battle) phase of what became known as the Battle of Britain. The aim was to draw out Fighter Command into dogfights by attacking Channel Shipping. Targeting British convoy systems, in July 1940 Sperrle's air fleet claimed 90 vessels sunk for approximately 300,000 tons—a third of this was claimed over August and September. The claims were widely optimistic. Only 35 ships were sunk during the Kanalkampf period. Sperrle was becoming disconcerted at the personnel, rather than aircraft, losses. Two days before Operation Eagle—scheduled for 13 August—he had lost two Gruppenkommandeur and a Staffelkapitän. Sperrle knew he could not afford to lose experienced officers at such a rate.