During the last week of July in 1943, The Eighth Air Force of the United States Army Air Forces(USAAF) launched an offensive against Germany in the form of air raids in which 1,000 combatants were either killed, injured, or went missing. The United States of America launched these air raids alongside the United Kingdom, which they called Operation Gomorrah. Hamburg was deemed an important strategic target due to its housing of U-boats and oil refineries in the region. Because the Nazis knew and understood the importance of Hamburg, the city was ringed with anti-aircraft weapons and 1,700 shelters were provided for its 230,000 citizens. To counter the radar use in Hamburg, British bomber crews applied strips of tin foil, known as Chaff, to the bomber which would be dropped to confuse the radar screen and would appear as a cluster of targets on the screen. Britain's first attack came on the 24th, with the USAAF to follow the next day, but they ran into difficulties navigating the city due to the large amount of smoke the RAF had caused on the night before.