The correct answer to this open question is the following.
The United States Marines raised the US flag on Mount Suribachi after the American victory in the Iwojima Battle on February 23, 1945. It was a bloody battle that represented an important victory for the United States and its Allies. The moment was captured by Joe Rosenthal in an expressive photograph that shows six US marines raising the flag. An impressive monument with based on that image can be visited in Washington DC.
Yes. This was part of a two day war in Iwo Jima that killed multiple American marines. The flag was raised to show American forces had defeated the Japanese forces who fought hard and vigorously