Chinese President Xi Jinping has met Indian Prime Minister Narendra Modi three times in the past three years. Indian pilgrims are back at Kailash, the Tibetan mountain sacred to Hindus and Buddhists. Air China has restarted flights to New Delhi. But can trust grow between two armies that meet only in a crisis? And why does the Pentagon now talk to the People’s Liberation Army (PLA) more easily than India’s army does? In September, Xi made his first visit to India in nearly seven years; Beijing...