---
title: "Alliances in International Relations | Model Diplomat"
description: "Alliances are agreements between states for mutual military support against threats. Key for Model UN students and policy researchers."
url: "https://modeldiplomat.com/learn/glossary/alliances"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- Alliances are formal or informal agreements between sovereign states to coordinate security policy, typically promising mutual military assistance against a common adversary.
- What is the difference between balance-of-power and balance-of-threat theory in alliance formation?
- What is the legal basis for modern collective-defence alliances?
- Why does India avoid formal military alliances?
- What is the alliance security dilemma?

[Civil Service & Diplomatic Exams](https://modeldiplomat.com/learn/civil-services/glossary)Updated June 22, 2026

Alliances are formal or informal agreements between sovereign states to coordinate security policy, typically promising mutual military assistance against a common adversary.

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In 2023 Finland abandoned decades of military non-alignment to join NATO under the North Atlantic Treaty's Article 5 collective-defence guarantee, directly in response to Russia's 2022 invasion of Ukraine.

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