“Dhimmitude,†like takfir and sharia, is a word of which Americans were happily ignorant not so long ago. Events, unfortunately, have expanded our Arabic vocabulary. As with other Islamic concepts, the meaning of dhimmitude, even its existence, is contested among Muslims. And misuse is not always merely semantic for those prone to issuing fatwas.No matter how nuanced the definition, dhimmitude always entailed a degree of subordination under Muslim rule. Historically, the dhimmi accepted second-class status as an alternative to conversion, death, or enslavement. For the privilege of being tolerated in lands under the Prophet’s sway, Christians, Jews, Hindus—any infidel—renounced...