Complex sentence: Political dissenters were eliminated by arrest, torture, and execution, and when the Muslim Brotherhood mounted a rebellion in Hama in 1982, Assad suppressed it, killing between 10,000--25,000 people.
Split into simpler sentences: Political dissenters were eliminated by arrest, torture, and execution. When the Muslim Brotherhood mounted a rebellion in Hama in 1982, Assad suppressed it and killed 10,000--25,000 people.