The first firebombing attack in this campaign—codenamed Operation Meetinghouse—was carried out against Tokyo on the night of 9/10 March, and proved to be the single most destructive air raid of the war. XXI Bomber Command mounted a maximum effort, and on the afternoon of 9 March 346 B-29s left the Marianas bound for Tokyo. They began to arrive over the city at 2:00 am Guam time on 10 March, and 279 bombers dropped 1,665 tons of bombs. The raid caused a massive conflagration that overwhelmed Tokyo's civil defenses and destroyed of buildings, representing seven percent of the city's urban area. The Tokyo police force and fire department estimated that 83,793 people were killed during the air raid, another 40,918 were injured and just over a million lost their homes; postwar estimates of deaths in this attack have ranged from 80,000 to 100,000. Damage to Tokyo's war production was also substantial. Japanese opposition to this attack was relatively weak; 14 B-29s were destroyed as a result of combat or mechanical faults and a further 42 damaged by anti-aircraft fire. Following the attack on Tokyo, the Japanese government ordered the evacuation of all schoolchildren in the third to sixth grades from the main cities, and 87 percent of them had departed to the countryside by early April.