The Treaty of Southampton makes an alliance between England and the Dutch Republic against Spain.

The **Treaty of Southampton**, signed on **7 September 1625**, established a military alliance between **England and the Dutch Republic** against Spain during the wider struggle of the **Eighty Years’ War** and the early years of the **Thirty Years’ War**. The agreement was concluded during the reign of **King Charles I of England**, who had inherited from his father, James I, growing pressure to take a stronger stand against the Spanish Habsburgs. English hostility toward Spain had intensified after the failure of negotiations for Charles to marry the Spanish Infanta Maria Anna, while Protestant leaders in England were also eager to support the Dutch in their long fight for independence from Spanish rule.

Under the treaty, England and the Dutch Republic agreed to cooperate in military operations against Spain, particularly at sea. One of their principal objectives was to weaken Spanish naval power and disrupt the flow of wealth from Spain’s overseas empire, which helped finance Habsburg military campaigns in Europe. The alliance contributed to the planning of a major Anglo-Dutch expedition against **Cádiz** in southern Spain later in 1625. A large English fleet, supported by Dutch warships, was sent to attack the Spanish port and intercept the valuable Spanish treasure fleet returning from the Americas. However, the Cádiz expedition was badly organized and ended in an embarrassing failure, with disease, poor leadership, inadequate supplies, and indiscipline forcing the allied forces to withdraw.

Although the Treaty of Southampton demonstrated England’s determination to become more directly involved in the European conflict, the alliance did not produce the decisive results its supporters had hoped for. England soon became distracted by other conflicts, including war with France beginning in 1627, while Charles I faced increasing financial and political difficulties at home. Nevertheless, the treaty was significant because it marked a clear departure from the relatively cautious foreign policy pursued during much of James I’s reign. It also strengthened the long-standing connection between England and the Protestant Dutch Republic and placed England openly on the anti-Habsburg side of the European struggles that dominated the first half of the seventeenth century.