This happened 9th to 10th March 1945. A total of 279 low flying B-29 bombers dropped some 1000 tonnes of firebombs to Tokyo. Some 41 square kilometres of the city was burned and some 100,000 inhabitants got killed in the ensuing fire hell inferno. One million Japanese lost their homes.
The American losses were 14 B-29 bombers shot down, 19 written off and 42 damaged. Over 200,000 buildings were destroyed.
The firebombing of Tokyo is one of the reasons why there are very few historical buildings in Tokyo. Almost all buildings are from the post-war era. Compared to Kyótó or most European cities, Tokyo is architecturally very dull town.
What the USAAF didn't do was nuking Tokyo, and the reason is simple: after the Operation Meetinghouse there was nothing left to nuke any more in Tokyo.
More people were killed in Tokyo firebombing than Hiroshima and Nagasaki nukings combined. There were almost no buildings standing any more in Tokyo.