In 899, Atenulf I defeated Radelchis II and conquered Benevento. He was proclaimed Prince of Benevento in January 900. He united the principalities of Capua and Benevento and declared them to be inseparable. He also introduced a diarchy-style system for the throne. Under this system, the sons and brothers of the prince would have equal status, and would rule alongside the prince. By doing this, Atenulf hoped to prevent future disputes over succession.