The second event was the outbreak of the Boeotian War, directly caused by the Spartan intervention in Thebes. In 378 BC, some of the exiles from this intervention returned to Thebes and assassinated Leontiades, overthrowing the pro-Spartan tyranny. The Spartan governor sent for reinforcements, but they were destroyed during their approach by Theban cavalry. The cavalry then stormed the Theban acropolis and restored a popular anti-Spartan government. This led to war between Sparta and Thebes.