Complex sentence: On 9 August the Soviet invasion of Manchuria began and the Japanese Kwantung Army beat a quick retreat southward in their puppet state of Manchukuo, about which Bose was told on 10 August, and sometime earlier he was told about the atomic blasts in Hiroshima and Nagasaki.
Split into simpler sentences: On 9 August the Soviet invasion of Manchuria began and the Japanese Kwantung Army beat a quick retreat southward in their puppet state of Manchukuo. On 10 August, Bose was told about the atomic blasts in Hiroshima and Nagasaki.