Complex sentence: Despite the declarations, the decline of the links between the Kingdom of Poland and the Grand Duchy of Lithuania between 1440 and 1447 were broken and in 1447 were reintroduced as a personal union that lasted until 1492.
Split into simpler sentences: Despite the declarations, the decline of the links between the Kingdom of Poland and the Grand Duchy of Lithuania continued and were finally broken between 1440 and 1447. In 1447 the union was yet again reintroduced as a personal union that lasted until 1492.