Complex sentence: In August 2004, the African Union sent 150 Rwandan troops in to protect the ceasefire monitors, however it soon became apparent that 150 troops would not be enough so they were joined by 150 Nigerian troops.
Split into simpler sentences: In August 2004, the African Union sent 150 Rwandan troops in to protect the ceasefire monitors. However, it soon became apparent that 150 troops would not be enough, so they were joined by 150 Nigerian troops.