As a young boy, I asked my father what the cause was for the collapse of the Polish-Lithuanian Commonwealth and its partitioning by its imperialistic neighbors. He quick answer was, "Liberum veto". The liberum veto was a form of an unanimity rule whereby one member of the Sejm could effectively overturn passed legislation. It was first used in 1669 and by the mid-18th Century, through strategically placed bribes, it was a useful tool for Czarist Russia and Prussia to frustrate reforms and weaken the Polish-Lithuanian Commonwealth.
By 1768, the influence of Czarist Russia on the Polish Sejm threatened its internal and external independence. A number of nobles and patriots were unwilling to be bystanders to the coming national catastrophe. They gathered at the fortress at Bar in 1768 and formed a legal military association intent on preserving the Polish-Lithuanian Commonwealth.
The inevitable civil war began shortly thereafter and Russian troops soon entered the Commonwealth in support of King Stanislaw Poniatowski. In 1771, King Poniatowski was kidnapped but quickly liberated. However, he claimed that Casimir Pulaski and the Bar Confederation were his abductors, a charge that Casimir Pulaski denied to his dying day. Public support for the Bar Confederation quickly waned after the accusation.
On 28 April 1772 Wawel Castle in Krakow surrendered. On 13 July 1772, Tyniec near Krakow fell. On 18 August 1772, the monastery fortress at Czestochowa capitulated. The last bastion, the monastery at Zagorz, gave up on 28 November 1772.
Weakened further by the civil war, the Polish-Lithuanian Commonwealth was now ripe for partitioning. Stanislaw August Poniatowski would be the last Polish king.