ISIS is the very definition of a fundamentalist religious group. Religious fundamentalism is nothing new in the modern era, and not unique to Islam. Christians and Jews, to say nothing of Hindus, each have their groups that seek to live in accordance with laws and scripture that date back thousands of years. Each has had their zealots who have committed terrible crimes. Each embraces practices that many view to be medieval. Christianity has a strong millennialist tradition, mirrored or even rooted in Judaism, that suggests that a return to the fundamentals of faith will presage the end of days and the second coming, a stance that is widely embraced in Iran, notably by former President Ahmadinejad. ISIS is not unique in its fundamentalism or its apocalyptic vision, but rather in its dictates to conquest that the Prophet — himself a general — set forth in his foundational work.