Alliance

An alliance is a formal or informal partnership in which political actors coordinate to pursue shared purposes, often security. It can bind states, parties, or other political groups without merging them.

Collective defense: A security arrangement in which members treat an attack on one as a concern for all. Some alliances make mutual defense their central obligation.
NATO: A transatlantic political and military alliance founded in 1949. NATO is a prominent example of a treaty-based collective-defense alliance.
Collective security: A system in which states jointly oppose aggression against any member, rather than targeting a specified outside threat. Unlike most alliances, it is designed to include a broad community rather than a selected coalition.
Balance of power: A distribution of capabilities in which no actor can dominate the others. Alliances can aggregate power to counter a stronger state or coalition.
Realism (international relations): A family of international-relations theories emphasizing power, security, and competition among states. Realist accounts explain alliances as responses to threats and shifts in power.
Deterrence: A strategy that seeks to prevent an action by threatening unacceptable costs or denying its benefits. An alliance can deter attack by combining members’ capabilities and signaling shared resolve.
Warsaw Pact: A Soviet-led military alliance formed in 1955 and dissolved in 1991. Its members’ formal commitments accompanied Soviet dominance in Eastern Europe.
Coalition: A temporary partnership formed to pursue a specific shared objective. Coalitions often end with a campaign or issue, while alliances may persist across changing tasks.
Security dilemma: A cycle in which one actor’s defensive measures make others feel less secure and respond in kind. An alliance intended as protection can appear threatening to states outside it.
Balance of threat: The theory that states align against perceived threats shaped by power, proximity, offensive capability, and intentions. It explains why states may align against a threatening neighbor rather than the strongest power.

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