Starting in August 1942 the United States and United Kingdom started waging a strategic bombing offensive against Germany. Throughout the course of the 1942 and 1943 campaigns, American and British air forces struggled to gain the upper hand in the European air war. By November 1943 American and British defeats at the hands of the German Air Force, or Luftwaffe, had placed the air war in doubt. By February 1944, the air war had turned around in favor of the Allies. This dramatic turn of events has been explained by historians in a number of ways. The most popular narrative is that the introduction of the long range escort fighter, the P-51 "Mustang," turned the tide in the air war. Another narrative is that there was a change in the fighter tactics. Starting in January 1944, American fighters stopped defending the bombers and started aggressively pursuing German fighters. Yet, these analyses do not include a major command changes that took place from November to January 1944. After his appointment to command of Supreme Headquarters Allied Expeditionary Force, General Dwight D. Eisenhower used his position centralize all of the major air commands in Europe under his control. By unifying the air commands, the Allies were able to better coordinate and concentrate their air against Germany. In February 1944 the Allies focused their air forces against the Luftwaffe ultimately wearing down German fighter strength. After finally removing a major obstacle impending the strategic air war against Germany, the Allies concentrated their air forces against transportation and oil targets. The destruction of these two major economic systems crippled Germany's ability to fight the Allies in 1944 and 1945. By changing the command structure, Eisenhower was able to use his air forces in successful coordinated strategic air offensives that the Allies had previously been incapable of accomplishing.