The Treaty of Berwick was a pivotal agreement that outlined the conditions under which English military forces were allowed to intervene in Scottish affairs, particularly to oust French troops that had been sent to support the Catholic Mary, Queen of Scots. The Lords of the Congregation, a group of Protestant nobles, sought assistance from England to regain control from the French and the Scottish Catholic faction loyal to Mary. This treaty was signed in Berwick-upon-Tweed, a town with strategic significance due to its location on the Anglo-Scottish border.

Negotiated amidst the backdrop of the Reformation and rising tensions between Protestant and Catholic factions in Europe, the treaty reflected England's ambitions to expand its influence in Scotland and counteract French interests. The arrangement facilitated a complex military campaign that emphasized England's role as an ally to Scottish Protestants and marked a significant shift in Scottish governance, leading to further unraveling of Mary’s power. The treaty included provisions for mutual defense, outlining how English troops would assist in Scottish military actions against French forces.

The signing of the Treaty of Berwick set in motion events leading to a more pronounced English involvement in Scottish affairs and catalyzed the political landscape in Scotland, which was already fraught with internal divisions. The English military presence would further deepen the rift between the Protestant factions and the Crown, eventually leading to Scotland's acceptance of international assistance and the redefining of its sovereignty within a European context.