Complex sentence: This league consisted of teams from American military bases throughout Europe, with one of the league's three conferences made up of teams based in the UK--teams from this conference won the league championship thirteen times until the competition ceased in 1993.
Split into simpler sentences: This league consisted of teams from American military bases throughout Europe, with one of the league's three conferences made up of teams based in the UK. British-based teams won the league championship thirteen times until the competition ceased in 1993.