Causes of War in Latin America Explained: Definitions, History, and Future

From key trends to fundamental details, understand everything about Causes of War in Latin America Explained: Definitions, History, and Future in our latest feature.

The historical evolution of international law has aimed to narrow the legal room for declaring an unprovoked casus belli. Following the devastation of World War I, the Kellogg-Briand Pact of 1928 formally outlawed war as an instrument of national policy. While it lacked robust enforcement mechanisms, it fundamentally dismantled the long-standing international legal norm that sovereign states had an absolute, discretionary right to wage war whenever they suffered a perceived slight.

The modern legal order rests on the foundational principles of the United Nations system:

• Prohibition of Aggressive War: The UN Charter binds all members under collective security. No border skirmish, economic dispute, or diplomatic insult can legitimately grant a nation the right to declare war unilaterally.
• The Threshold of "Armed Attack": Under Article 51, the right to self-defense is strictly triggered by an actual armed attack against a state's territory, airspace, or vessels. Minor cross-border incidents do not legally justify full-scale offensive campaigns.
• Proportionality and Necessity: Under customary international humanitarian law, any military response to a provocation must remain both necessary to halt the threat and strictly proportional to the harm suffered.
• The ICC Crime of Aggression: Since the operationalization of the Kampala amendments in 2018, individuals in high-ranking leadership positions can be held criminally liable for planning, initiating, or executing an act of aggression that blatantly violates the UN Charter.

These legal guardrails have fundamentally altered how state leaders frame their foreign policy. Rather than openly citing a traditional casus belli, modern states frame military maneuvers under the rubric of anticipatory self-defense, humanitarian intervention, or stabilization mandates. The terminology changes, but the core political incentive remains identical: states continue searching for a legally defensible justification whenever they deploy lethal force across an international border.