This week’s summit between Prime Minister Narendra Modi and US President Donald Trump will be a paradoxical moment in the diplomatic history between the two nations. It is a moment of continuity and discontinuity; it is about India dealing with a familiar leader who is moving America into unfamiliar terrain. India had a good run with President Trump in his first term, and Delhi is now dealing with a different leader. Modi and External Affairs Minister S Jaishankar have negotiated many tricky waters over the last decade and will hopefully get this one right, too. India’s quick diplomatic work over...