Complex sentence: He became even more involved after the Maseru Massacre of December 1982, when South African Defence Force commandos attacked a cluster of houses in Maseru which they believed was where African National Congress exiles were hiding.
Split into simpler sentences: He became even more involved after the Maseru Massacre of December 1982. This is when South African Defeence Force commandos attacked a cluster of houses in Maseru which they believed was where African National Congress exiles were hiding.