Complex sentence: Most of the lands of the former Grand Duchy were reannexed by Russia, Augustów Voivodeship (later Augustów Governorate), including Marijampolė and Kalvarija Counties, was attached to the Kingdom of Poland, a rump state in personal union with Russia.
Split into simpler sentences: Most of the lands of the former Grand Duchy were re-annexed by Russia. The Augustów Voivodeship (later Augustów Governorate), including the county of Marijampolė and Kalvarija, were attached to the Kingdom of Poland, a rump state in personal union with Russia.