Complex sentence: During the division's push to Baghdad, Mattis relieved Colonel Joe D. Dowdy, regimental commander of Regimental Combat Team-1, and it was such a rare occurrence in the modern military that it made the front page of newspapers.
Split into simpler sentences: During the division's push to Baghdad, Mattis relieved Colonel Joe D. Dowdy, commander of Regimental Combat Team-1. It was such a rare occurrence in the modern military that it made the front page of newspapers.