Simplify the following text for a Grade 8 native English-speaking person.
Original: Most of the detainees were captured Japanese and Italian military personnel , On August 5 , 1944 , at least 545 Japanese POWs attempted a mass breakout from the camp .
Simplified: On August 5 , 1944 about 545 ( some sources say over 1000 ) Japanese POWs attempted a mass escape from the camp .