Why did Truman decide against invading Japan?

President Harry Truman decided against invading Japan primarily due to the anticipated high casualties that such an operation would incur for both American forces and Japanese civilians. Military estimates suggested that an invasion could result in hundreds of thousands of American deaths and potentially millions of Japanese casualties. Additionally, the use of atomic bombs on Hiroshima and Nagasaki demonstrated a faster means to end the war, leading to Japan's surrender without the need for a costly invasion. This decision was influenced by the desire to minimize loss of life and expedite the conclusion of World War II.