The Commonwealth of Poland-Lithuania, also known as the Polish-Lithuanian Commonwealth, was a dual state formed in 1569 through the Union of Lublin. It united the Kingdom of Poland and the Grand Duchy of Lithuania, creating one of the largest and most populous countries in Europe at the time. The Commonwealth was characterized by a unique political system that allowed for a degree of self-governance and religious tolerance. The Commonwealth reached its peak in the late 16th and early 17th centuries, becoming a major cultural and political force in Europe. However, it faced challenges such as internal conflicts, wars, and external pressures from neighboring powers like Russia, Prussia, and Austria. The Commonwealth ultimately declined and was partitioned in the late 18th century, leading to its dissolution.