The Protestant Union was formed in 1608, primarily to protect the interests of Protestant states within the Holy Roman Empire against the increasing influence and military power of the Catholic League. It was established amidst growing tensions following the Reformation, which had led to a division between Catholic and Protestant territories in Europe. Key leaders like Elector Palatine Frederick V played significant roles in uniting these Protestant states to defend their religious and political rights.

However, the dissolution of the Protestant Union was precipitated by the devastating defeat suffered at the Battle of White Mountain in 1620 during the early phases of the Thirty Years' War. This battle marked a crucial turning point, as the forces of the Catholic League decisively defeated the Protestant Bohemian army, resulting in the solidification of Catholic power and foreshadowing further military engagements between the two factions across Europe. Following this defeat, many Protestant leaders recognized the futility of continued resistance against the better-organized and better-supported Catholic forces, leading to a decline in Protestant unity and morale.

On May 24, 1621, the official dissolution took place, signaling a critical juncture for Protestant states within the Holy Roman Empire. The disbanding of the union meant that individual states would now have to navigate their tumultuous relationships with both the Catholic League and each other. As a result, many Protestant states faced isolation, further weakening their ability to resist future Catholic advancements during the Thirty Years' War, which lasted until 1648.