This is the reality: A career diplomat crossing European borders in a rented car while carrying a professionally-made bomb, which bears a design favored by jihadists. In Luxembourg, he hands over the bomb to two would-be terrorists, long-standing residents of Europe who just look like any ordinary young married couple. They accept it with a clear mission in mind: to bomb a political rally in the largest convention center in France, located in the suburbs of Paris. If the plot is successful, it will kill many among the tens of thousands of people in attendance, among who were hundreds of...