Following the First Partition of Poland in 1772, in an attempt to strengthen the significantly weakened Commonwealth, King Stanisław August Poniatowski put into effect a series of reforms to enhance Poland's military, political system, economy, and society. These reforms reached their climax with the enactment of the May Constitution in 1791, which established a constitutional monarchy with separation into three branches of government, strengthened the bourgeoisie and abolished many of the nobility's privileges as well as many of the old laws of serfdom. In addition, to strengthen Poland's international standings, King Stanislaus signed the Polish-Prussian Pact of 1790, ceding further territories to Prussia in exchange for a military alliance. Angered by what was seen as dangerous, Jacobin-style reforms, Russia invaded Poland in 1792, beginning the War in Defense of the Constitution. Abandoned by her Prussian allies and betrayed by Polish nobles who desired to restore the privileges they had lost under the May Constitution, Poland was forced to sign the Second Partition of Poland in 1793, which ceded Dobrzyn, Kujavia, and a large portion of Greater Poland to Prussia and all of Poland's eastern provinces from Moldavia to Livonia to Russia, reducing Poland to one-third of her original size before the First Partition.