Greece invaded Bulgaria over a stray dog — the 'War of the Stray Dog' lasted 10 days before the League of Nations forced a humiliating retreat.
In October 1925, a Greek soldier allegedly chased his dog across the Bulgarian border, where Bulgarian sentries shot him dead. A second version claims Bulgarian soldiers attacked a Greek outpost — no one ever agreed on what actually started it.
General Theodoros Pangalos issued a furious 48-hour ultimatum demanding a formal apology, punishment of those responsible, and two million French francs in compensation. When Bulgaria didn't satisfy him fast enough, Greek troops crossed the border and occupied the town of Petrich.
Bulgaria, knowing it couldn't match Greece militarily, made a calculated decision: rather than fight back, it appealed directly to the League of Nations. It was one of the earliest successful uses of international arbitration to stop a military invasion in progress.
The League of Nations ordered an immediate Greek withdrawal within 24 hours. Greece complied but was furious — Pangalos had expected to absorb Petrich without consequence. The League fined Greece, awarding Bulgaria £45,000 in reparations.
The conflict lasted just 10 days, from October 19–29, 1925. Despite its brevity and absurd origins, it killed around 50 Bulgarian civilians and 121 Greek soldiers — a reminder that even the smallest wars have real costs.
The incident became a landmark case demonstrating that the League of Nations could actually compel a member state to back down from aggression — something it would catastrophically fail to do just a decade later with Italy's invasion of Ethiopia.