During World War II, the British used Chittagong as an important frontline military base in the Southeast Asian Theater. Frequent bombardment by the Japanese Air Force, notably in April 1942 and again on 20 and 24 December 1942, resulted in military relocation to Comilla. It was a critical air, naval and military base for Allied Forces during the Burma Campaign against Japan. The Imperial Japanese Air Force carried out air raids on Chittagong in April and May 1942, in the run up to the aborted Japanese invasion of Bengal. British forces were forced to temporarily withdraw to Comilla and the city was evacuated. After the Battle of Imphal, the tide turned in favor of the Allied Forces. Units of the United States Army Air Forces Tenth Air Force were stationed in Chittagong Airfield between 1944 and 1945. American squadrons included the 80th Fighter Group, which flew P-38 Lightning fighters over Burma; the 8th Reconnaissance Group; and the 4th Combat Cargo Group. Commonwealth forces included troops from Britain, India, Australia and New Zealand. The war had major negative impacts on the city, including the growth of refugees and the Great Famine of 1943.