Complex sentence: Until 1944, the dioceses of Down and Dromore were part of the United Dioceses of Down, Connor and Dromore, often referred to as Down and Connor, but in 1944 the Diocese of Connor gained a separate existence under its own bishop.
Split into simpler sentences: Until 1944, the dioceses of Down and Dromore were part of the United Dioceses of Down, Connor and Dromore. In 1944, the Diocese of Connor gained a separate existence under its own bishop.