The Commonwealth was able to sustain the levels of prosperity achieved during the Jagiellonian period, while its political system matured as a unique noble democracy with an elective monarchy. From the mid-17th century, however, the huge state entered a period of decline caused by devastating wars and the deterioration of its political system. Significant internal reforms were introduced in the late 18th century, such as Europe's first Constitution of 3 May 1791, but neighboring powers did not allow the reforms to advance. The existence of the Commonwealth ended in 1795 after a series of invasions and partitions of Polish territory carried out by the Russian Empire in the east, the Kingdom of Prussia in the west and the Habsburg Monarchy in the south. From 1795 until 1918, no truly independent Polish state existed, although strong Polish resistance movements operated. The opportunity to regain sovereignty only materialized after World War I, when the three partitioning imperial powers were fatally weakened in the wake of war and revolution.