alliance

An alliance is a formal agreement among two or more states, or among organizations, to pursue shared objectives and to provide mutual support in specified domains. Alliances are usually established by treaties that set out purposes, membership, duration, obligations, and procedures for consultation and decision-making. They may be bilateral or multilateral and can cover military defense, economic cooperation, political coordination, or scientific collaboration. Agreements typically include mechanisms for dispute resolution and for adapting to changing threats or opportunities, including withdrawal or modification clauses.

Military alliances aim to deter aggression, reassure partners, and pool resources for defense. They are typically more durable and legally binding than ad hoc coalitions, yet they stop short of political union, with sovereignty remaining with each member. Economic and political alliances seek to align trade rules, standards, or regulatory policies, facilitate interoperability, and coordinate diplomacy. Some alliances function primarily as security dialogues or shared norms rather than force commitments.

Notable examples include NATO, a collective-defense alliance formed in 1949; the Warsaw Pact, established in 1955 and dissolved in 1991; and various regional arrangements that coordinate security, trade, or diplomatic positions. The modern landscape also features partnerships, blocs, and unions that blend elements of defense, trade, and governance. Alliances shape international behavior by signaling commitments, influencing deterrence, and affecting the costs and benefits of cooperation or conflict.