 Complete the following phrase:  The air war changed considerably in the first months of 1943. Fighter Command continued its offensive over Northwest Europe with growing numbers of the Spitfire IX ending the performance superiority of the Fw 190 A. Bomber Commands area offensives began in earnest with the Battle of the Ruhr and attack on Hamburg and the US Eighth Air Force, operational since mid-1942, was in sufficient strength to strike into Germany in January 1943 beginning the Combined Bomber Offensive, which began to grind down Luftwaffe strength. In North Africa, the Axis collapsed in May, having expended enormous manpower and material strength to hold African and Mediterranean positions while providing US forces with invaluable experience and intelligence on the quality of their enemy. The same month, Black May in U-boat campaign ensured the German navy could no longer alter the course of the war. On the Eastern Front, the defeat at the 