Complex sentence: The Japanese attack force for the invasion of Malaya, from Lieutenant General Tomoyuki Yamashita's 25th Army, had sailed from Samah Harbour on Hainan Island on 4 December 1941.
Split into simpler sentences: The Japanese attack force was draww from Lieutenant General Tomoyuki Yamashita's 25th Army. It sailed from Samah Harbour on Hainan Island on 4 December 1941.