In 1879, Chilean armed forces occupied the port city of Antofagasta after Bolivia threatened to confiscate the Chilean Antofagasta Nitrate Company's property.
Peru attempted to mediate, but when Bolivia announced that a state of war existed, the situation deteriorated.
In World War I, the treaties between Italy and Austria-Hungary, and Romania, which purportedly required Italy and Romania to come to Austria's aid if Austria was attacked by another nation, were ignored by both Italy and Romania because, as Winston Churchill wrote, "the casus fœderis had not arisen" since the attacks on Austria had not been "unprovoked.
"[1] Article 5 of the North Atlantic Treaty governs mutual defense in the event of an attack on a member nation.
[2] Where a political-military alliance pact is lacking, there is no obligation to intervene militarily alongside those asking for help, as the decision depends exclusively on the discretionary choices of foreign policy of the requested State.