Complex sentence: While traditionally Prussian, with the Second Peace of Thorn in 1466 the area became part of the Kingdom of Poland until 1772; 1772-1945 Kingdom of Prussia and Germany (East Prussia).
Split into simpler sentences: While traditionally Prussian, with the Second Peace of Thorn in 1466 the area became part of the Kingdom of Poland until 1772. From 1772 until 1945 it was held successively by the Kingdom of Prussia and Germany (East Prussia).