From January to July 2006, rival Philadelphia-based promotions Ring of Honor and Combat Zone Wrestling were involved in an interpromotional feud. The two promotions were natural rivals with their different style of wrestling, ROH being based on traditional and scientific wrestling, while CZW was known for their “ultraviolent” hardcore matches. The feud was well received by fans and critics alike, and is considered by many to be the greatest feud in ROH history.