Even more serious, the Germans had poor intelligence and little idea of British vulnerabilities. They wasted most of July in waiting for a British surrender and attacked only in August. Although air strikes did substantial damage to radar sites, on August 13–15 the Luftwaffe soon abandoned that avenue and turned to attacks on RAF air bases. A battle of attrition ensued in which both sides suffered heavy losses (an average loss of 21 percent of the RAF’s fighter pilots and 16 percent of the Luftwaffe’s fighter pilots each month during July, August, and September).
For a time the advantage seemed to swing slightly in favor of the Germans, but a combination of bad intelligence and British attacks on Berlin led the Luftwaffe to change its operational approach to massive attacks on London. The first attack on London on September 7 was quite successful; the second, on September 15, failed not only with heavy losses, but also with a collapse of <span>morale among German bomber crews when British fighters appeared in large numbers and shot down many of the Germans. As a result, Hitler permanently postponed a landing on the British Isles and suspended the Battle of Britain.</span>