This paper's argument is two-fold. First, the concepts of "partnership" and "alliance" deserve to be unpacked because they can reflect very different motivations and realities. Second, strategic partnerships do not exclusively take the form of a threat or an adversary-based alliance. Partnerships that are driven commonalities in political culture-"natural alliances"-can also be the expression of a very pragmatic approach to international relations, especially for leaders in search of predictability in an uncertain global landscape. This paper provides a categorization of alliances by identifying three drivers for state alignments: tactics, history and commonalities in political culture. It presents a discussion of the last driver-commonalities in political culture-and a methodology to identify natural alliances that the author applies to the US-European partnership. He find that the trans-Atlantic partnership forms a natural alliance since 1991 at least, which could potentially include Australia, New Zealand, Japan and South Korea but not Turkey. Understanding the differences between the driving forces of alliances has policy implications for the United States and European powers, especially as they seek to redefine the purpose of their partnership in the 21st century international landscape. Rather than being a necessary source of confusion, the diversity of alliances can potentially offer greater leverage to trans-Atlantic partners, through an appropriate mix of alliances fulfilling different purposes in a broad strategy. .

"Supported by the French Ministry of Defense"--T.p.

Introduction -- Categorizing strategic partnerships -- Identifying natural allies -- Policy implications -- Appendix: Identifying natural partners in the transatlantic community.