The Polish Kingdom refers to a historical state that existed in Central Europe, primarily during the Middle Ages. It was established in the 10th century and became a significant political entity under the rule of the Piast dynasty. The kingdom expanded its territory and influence, particularly during the reign of Casimir III the Great in the 14th century. In 1569, the Polish-Lithuanian Commonwealth was formed, merging the Polish Kingdom with the Grand Duchy of Lithuania. This union created one of the largest and most populous countries in Europe at the time. The Commonwealth lasted until the late 18th century when it was partitioned by neighboring powers, leading to the dissolution of the Polish state.