Alliances and Partnerships

Alliances and partnerships describe the formal and informal relationships the United States builds with other countries to deter threats, share the burden of defense, and coordinate military action when conflicts arise. These arrangements range from binding mutual defense treaties to looser security cooperation agreements, and they shape where American troops are stationed, how wars are fought jointly, and what the country owes its partners when danger appears.

Formal treaties and legal frameworks give alliances their teeth. Understanding how a mutual defense obligation actually works, and how it differs from other kinds of international agreements, helps explain why some crises trigger automatic military commitments and others do not; see Understanding Security Alliances vs. Economic Partnerships. When American forces are stationed on another country’s soil, a separate set of legal arrangements governs their conduct, covered in Status of Forces Agreements (SOFA) Explained.

Strategy and doctrine explain why alliances take the shape they do. Nations choose between collective security arrangements and older balance-of-power approaches, a distinction laid out in Understanding Collective Security vs. Balance of Power: How Nations Strive for Peace. The Department of Defense carries much of this strategy into practice, from joint training to long-term basing decisions, discussed in International Military Alliances: The Department of Defense’s Role and DoD International Relationships and Security Cooperation.

Readiness and coordination keep alliances functional between crises. Joint military exercises let allied forces practice working together before they ever need to fight together, a topic explored in Military Exercises: Purpose and Examples.