Complex sentence: Derby's national tour became so successful that by 1969, the Bay Bombers were broken up into a San Francisco and Oakland team, two units, which filled arenas across the country from 1969 thru 1971, when a third unit was added.
Split into simpler sentences: Derby's national tour became so successful that by 1969, the Bay Bombers were broken up into a San Francisco and Oakland team. These two units filled arenas across the country from 1969 through 1971, when a third unit was added.