According to ... reports, the North Korean Ministry of Industry’s underground offices were destroyed and a direct hit on another shelter was said to have killed 400 to 500 Communist officials. Off the air for two days, Radio Pyongyang finally announced that the ‘brutal’ strikes had destroyed 1,500 buildings and had inflicted 7,000 casualties.[236] [236] Futrell, _USAF, Korea_, p. 482. Of the far-reaching effect of the leaflets, the UN commander later wrote: The warning leaflets, coupled with the bombing, hurt North Korean civilian morale badly. The very audacity of the United Nations in warning the Communists where bombers would strike hurt morale because it emphasized to the North Koreans just how complete was UN mastery of the air. Contrarily, it made them see even more clearly that the Communists were ineffectual in their efforts to ward off our air blows.... As a result of the warnings, the bombings, the failure of the Communists to provide protection, and the refusal of the Communists to permit evacuation of the clearly defined target areas, civilian resentment was channeled away from the UNC bombers and towards the Communist rulers.[237] [237] Clark, _Danube to Yalu_, p. 209. “I told you so” leaflets were dropped after the raid to impress the inhabitants with the importance of believing the warning leaflets. USAF, _Ops in Korea_, No. 127, pp. 36, 37. The record set by the 1,254 sorties flown in this 11 July operation was to last only seven weeks. On 29 August, 1,403 sorties were employed in a new strike against the Capital. The massed raids against military targets in Pyongyang, known as the “All United Nations Air Effort” turned out to be the largest one-day air assault during the entire three years of the Korean War. Again attacking at four-hour intervals three times during daylight, Allied aircraft blasted a list of targets that “read like a guide to public offices in Pyongyang and included such points of interest as the Ministry of Rail Transportation, the Munitions Bureau, Radio Pyongyang, plus many factories, warehouses, and troop billets.”[238] Of the 45 military targets in the city, 31 received moderate-to-severe damage according to post-strike photographs. [238] Futrell, _USAF, Korea_, p. 489.