In summer of 1721, a large earthquake shocked Tabriz, killing about eighty thousand of its residents. The devastation continued in 1724–1725, when the city was invaded by an Ottoman army. During this round of invasion, the Ottomans imprisoned many in Tabriz and killed about two hundred thousand residents. The city was subsequently retaken by the Iranian army, after which a widespread famine, combined with the spread of fatal diseases, killed more of those who still remained. In 1780, a major earthquake hit near Tabriz and killed as many as two hundred thousand people, leaving only about thirty thousand survivors.