Signed on 21 May 1420, the Treaty of Troyes represented a pivotal moment in the Hundred Years' War, fundamentally altering the dynastic landscape of Western Europe. Under the terms of this agreement, Henry V of England was formally recognised as the heir and regent to the French throne, effectively disinheriting the Dauphin, Charles. This diplomatic achievement was further solidified by the marriage of the English monarch to Catherine of Valois, the daughter of King Charles VI of France, which sought to unite the two crowns under a single Anglo-French dual monarchy.

The treaty emerged from the protracted struggle over royal authority and competing territorial claims that defined late-medieval Anglo-French relations. By securing his position as the successor to the French crown, Henry V aimed to bring a definitive end to the long-standing conflict, though the arrangement faced significant resistance from those loyal to the Dauphin. The political ramifications of this union were profound, influencing the trajectory of governance, military strategy, and the development of national identity in both kingdoms.

Beyond its immediate political impact, the Treaty of Troyes serves as a critical lens through which to examine the broader transformations occurring in medieval society. The event highlights the complex interplay between dynastic ambition, religious legitimacy, and the evolving nature of the state during the fifteenth century. Its legacy offers insight into the following areas of historical change:

• The shifting nature of royal authority and legitimacy in medieval Europe.
• The influence of dynastic marriage alliances on international diplomacy.
• The impact of prolonged warfare on social and political structures.
• The development of national consciousness amidst cross-channel conflicts.
• The challenges of maintaining a dual monarchy across disparate territories.

As a landmark in the history of the Late Medieval Britain period, the treaty remains a vital point of reference for understanding how England navigated its role on the continent. The subsequent collapse of the dual monarchy following the deaths of both Henry V and Charles VI only serves to underscore the fragility of the peace established at Troyes and the enduring volatility of the era.