Facing Spanish Habsburg rule, delegates from Holland, Zeeland, and other northern provinces formed a mutual defense pact that guaranteed religious tolerance and provincial autonomy while coordinating military and diplomatic policy. The union effectively split the Low Countries and became the de facto constitution of the Dutch Republic for the next two centuries.
The agreement was less a bold declaration of independence than a defensive contract among provinces exhausted by Spanish taxation and religious persecution under Philip II. Each province retained its own laws, courts, and even religious preferences—Holland leaned firmly Calvinist while other signatories kept more Catholic populations tolerated in practice.
William of Orange, the rebellion's reluctant figurehead, initially hesitated to fully endorse the union because it hardened the split with the southern provinces he still hoped to win back.
The Union's decentralized, almost improvised structure became a defining feature of Dutch governance. It produced a republic without a king, run by merchants and regents, that within decades would out-trade and outfight empires many times its size—proof that a patchwork alliance built on mutual suspicion could still outlast the monarchies it defied.