Simplify the following text for a Grade 10 native English-speaking person.
Original: Korea under Japanese rule or Japanese ruled in Korea was Korean was Colony of Japan 's 35-year imperialist expansion 22 August 1910 to 15 August 1945 .
Simplified: Korea was under Japanese rule as part of Japan 's 35-year imperialist expansion ( 22 August 1910 to 15 August 1945 ) .