Complex sentence: In 1944 Japan launched a massive invasion and conquered Henan and Changsha, but eventually surrendered on September 2,1945 after the atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Japanese-held Manchuria.
Split into simpler sentences: In 1944 Japan launched a massive invasion and conquered Henan and Changsha. Despite continuing to occupy Chinese territory, Japan eventually surrendered on September 2,1945 to Allied forces following the atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Japanese-held Manchuria.