- The M47 bombs dropped by pathfinder planes started fires which were spread rapidly by the high wind. Bombs from following planes started additional fires which later merged to form one vast mass of flame as viewed from the air. Planes which bombed during the latter part of the attack found visibility very poor and dropped bombs short of the target area. These bombs started fires in the congested industrial area south and east of Zone 1. (About 0.8 square mile of the total 11.08 square miles comprising the Zone 1 area had been burned in the attack of 25 February 1945.) The 9-10 March attack burned all of Zone 1 area east of and a major portion of Zone 1 area lying west of the Sumida River. Small areas in the extreme northwest top and a narrow strip running northwest in the south-western corner escaped damage (Photos 30 and 31, Figure 3). Few bombs hit these areas because the last planes over the target area had difficulty locating aiming points due to extensive fire and smoke. The total damage resulting from this single attack was 15.8 square miles of the heart of the city. Calculations indicate that about two-thirds of Zone 1 was burned along with about nine square miles of the great industrial area bordering Zone 1. Figures furnished by the Metropolitan Police Bureau show 267,171 buildings burned in this one attack. The Japan Year Book of 1944 stated that Tokyo had 1,057,921 buildings in 1938 of which 692,731 were dwellings. Based on these figures the attack of 9-10 March totally damaged about 25 percent of all buildings in Tokyo.
- The 28-mile-per-hour wind during the course of the attack which increased in velocity as the fires merged, contributed considerably to the intensity and further spread of the conflagration. The direction of the wind, north-northwest and north west caused the fire to spread to the highly congested tenement and industrial district east and south of Zone 1, resulting in considerable damage to industrial plants. Fire to the south and southeast burned itself out against open areas, the Diversion Canal or firebreaks. The fire west of the Sumida River burned itself out either against areas burned in the 25 February 1945 attack, or against the river. Isolated fires to the southwest and northwest caused by spill-overs were relatively small and were controlled by fire department operation and open areas.
- The highly combustible nature of the city resulted in an intense fire of short duration. Observers stated that the heat was so intense that entire block fronts burst into flames before the main body of the fire reached them. The heat intensity was indicated by the absence of smudges on concrete buildings. Combustible contents of buildings burned completely, leaving no evidence of what the contents may have been, and without marking the walls with smoke. The fire chief stated that the fire had burned itself out by morning except for fires in industrial buildings. An aerial photograph taken at about noon the following day (Photo 31) showed few fires still burning. No data were available on the temperatures reached, but considerable melted glass and, in one case, melted concrete were noted (Photos 32, 33 and 34).