Complex sentence: The first wave began with simultaneous raids in Karbala and Diwaniyah on militia forces, followed by a second wave on May 5 in Karbala and more attacks that seized the governor's office in Najaf on May 6.
Split into simpler sentences: The first wave began with simultaneous raids in Karbala and Diwaniyah on militia forces. It was followed by a second wave on May 5 in Karbala, and more attacks which seized the governor's office in Najaf on May 6.