The Mutual Assistance Clause of the Treaty of Nancy and the Problem of Trust Formation in Franco-Polish Relations
The Mutual Assistance Clause of the Treaty of Nancy and the Problem of Trust Formation in Franco-Polish Relations

Summary/Abstract: The Treaty on Enhanced Cooperation and Friendship between the Republic of Poland and the French Republic, signed in Nancy on 9 May 2025 and entering into force on 22 January 2026, marked a significant deepening of bilateral relations. Concluded against the background of acute threats to European security generated by the war in Ukraine, the treaty establishes a comprehensive framework for bilateral cooperation, including in the area of security and defence; among the provisions concerning this area, the mutual assistance clause in case of armed aggression was singled out by the signatories of the treaty as the most consequential provision. As the logic of the treaty and the statements of its signatories suggest, the force of this clause stems not merely from its formal statement but from its grounding in the mutual trust built through a long history of Franco-Polish solidarity and, no less importantly, through the honest acknowledgment of major failures along the way. The paper proceeds in three stages. The first section outlines the reasons for the commitment of both parties to the treaty, rooted in current geopolitical realities as well as in enduring principles of their respective foreign policies. The second analyses the mutual assistance clause in the context of the treaty’s broader defence provisions and assesses its added value for Franco-Polish relations. The third examines how shared history and mutual trust bear on the credibility of the mutual assistance clause, and to this end it draws on the text of the treaty, statements by its signatories, and scholarly literature on the relationship between trust, history, and defence commitments.

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