The Protestant Union was an alliance formed in 1608 among various Protestant states in the Holy Roman Empire. Its primary goal was to provide mutual defense against the growing power of the Catholic League, which was led by the Habsburg dynasty. The Union aimed to protect the rights and interests of Protestant territories during a time of religious conflict. The Protestant Union played a significant role in the early stages of the Thirty Years' War, which began in 1618. However, it struggled with internal divisions and was ultimately dissolved in 1621 after suffering military defeats, particularly at the Battle of White Mountain.