Complex sentence: In the late 1700s the Polish-Lithuanian Commonwealth began to collapse and it's neighbouring states were able to slowly dismember the State until 1795 when Poland's territory was completely partitioned among Kingdom of Prussia, Russian Empire and Austria.
Split into simpler sentences: In the late 1700s, the Polish-Lithuanian Commonwealth began to collapse. Its neighboring states were able to slowly dismember the Commonwealth until 1795, when Poland's territory was completely partitioned among the Kingdom of Prussia, the Russian Empire, and Austria.