What was the Bastille's primary function under the kings of France?

Under France’s kings, the Bastille’s primary function was a state prison.

The fortress was originally built in the late 14th century to defend Paris’s eastern approach during the Hundred Years’ War. Over time, however, its military importance declined as the city expanded and improved defenses changed the strategic value of the site. The monarchy increasingly used the Bastille to confine prisoners.

Detentions were often ordered through lettres de cachet, royal warrants that could send people to prison without a public trial. The inmates included political opponents, writers, nobles, religious prisoners, and people caught up in private disputes. Voltaire and the Marquis de Sade were among its well-known detainees, though conditions varied and the prison was not always overcrowded.

The Bastille still had military facilities and stored weapons, which helped make it a strategic target on 14 July 1789. Only seven prisoners were held there when revolutionaries captured it, but the fortress had become a powerful symbol of royal arbitrary rule.