President Barack Obama will visit India in January as the guest of honor for India’s symbolically important Republic Day celebrations—a sign of a significant warming of relations between the world’s two largest democracies. A tweet from Prime Minister Narendra Modi ’s verified account said, “we hope to have a friend over,” noting that Mr. Obama will be the first American president to attend the holiday, which is usually marked by a major military parade. The White House said, that Mr. Obama had accepted Mr. Modi’s invitation.