Complex sentence: The M23 rebellion was fighting that occurred between the March 23 Movement and the government of the Democratic Republic of the Congo (DRC) in North Kivu, beginning in 2004 after the formal end of the Second Congo War in 2003.
Split into simpler sentences: The M23 rebellion was fighting in North Kivu, Democratic Republic of the Congo (DRC), that occurred between the March 23 Movement and government forces. The rebellion broke out in 2004 after the formal end of the Second Congo War in 2003.