Aziz’s story helps us understand why this battlefield is closer to home than we might imagine. Long before the Islamic State emerged as a platform for jihadists in the region, Islamist ideologues and military commanders shared experiences and resources to spread their movement across borders. The growing influence of the Islamic State in Central Asia could give renewed momentum to the jihadist movement in India, too. Earlier this week, four ethnic Tajik jihadists linked to the Islamic State attacked the Crocus Theatre in Moscow, killing at least 130 people. Even though the savage killing will seem familiar to those who...