Efforts on another front were also productive. Prior to 1943 the Portuguese government only allowed German U-boats and navy ships to refuel in the Azores. However diplomatic efforts in 1943 persuaded Portuguese dictator Salazar to lease bases on Azores Islands to the British. This represented a change in policy and was a key turning point in the Battle of the Atlantic allowing the Allies to provide aerial coverage in the middle of the Atlantic. This helped allies to hunt U-boats, protect vital convoys and support mid-Atlantic Air Transport Command ferry efforts.