What battle had most casualties for the US in the pacific in World War 2?

Answer 1

If civilians are included, and the US was involved, the retaking of the Philippines. Manila was declared an open city, but the commander of the 20,000 Japanese Marines there refused to leave, forcing a fight for the city, which possesses no military significance whatsoever. Upward of 100,000 Filipino civilians died in Manila, and the city was destroyed in rooting out the Japanese. Fighting was still going on in the Philippines when the war ended.

If civilians are included but the US was not involved, perhaps the "Rape of Nanking", where Japanese troops were given free rein to abuse the population for six weeks after the city was captured, out of peevishness for the resistance offered to the brave soldiers of Nippon. Over 300,000 Chinese civilians were slaughtered and every female who could be caught was raped, and usually shot immediately afterward.

In purely military casualties, Okinawa. Okinawa and the Philippines were the only two campaigns in the Pacific on islands large enough that the US was able to deploy an entire field army. There were some 80,000 defenders, who of course had to be killed to the last man. Okinawa was the pre-war home of the Japanese artillery school , and they had every inch of it registered for fire. There were times and places on Okinawa where a mans life expectancy could be measured in seconds.

I must respectfully disagree with the above answer. In purely allied military casualties, the greatist losses were "The battle of New Gunea" which encompassed Battle of Kokado Track and the Battle of Milne Bay fought predominately by the Australians and the massive losses at Buno and Gona which were downplayed but could have been as high as 21, 000.

Compared to the 12,000 lost in Okinawa, approx 7,000 in both Iwa Jima and Guadacanal

Answer 2

I believe it was the Battle of Okinawa.