Dönitz reacted by deploying his U-boats near the Azores where land-based aircraft still had difficulty reaching them. In this region he hoped to threaten the Gibraltar–Britain convoy route. Dönitz intended to concentrate his power in a rough arc from West Africa to South America and the Caribbean. He hoped to maintain a presence in the western and central Atlantic, reduce losses and await new weapons and anti-detection devices. In this, he failed to "stem the tide of U-boat losses." A large portion of the 39 U-boats deployed on these operations were intercepted. From May 1943, one historian wrote "U-boats rash enough to close with an Atlantic convoy...were simply inviting destruction."