Russia-China Bond Is Closely Watched, and Fraught

Birthday best wishes rarely come freighted with so much significance. But when it is Russia's embattled president, Vladimir V. Putin, flattering his Chinese counterpart, Xi Jinping, even seemingly small gestures send a message to the world, not least to their Western rivals. Mr. Putin sent Mr. Xi a congratulatory telegram when the Chinese leader turned 70 on Thursday, wishing his "dear friend" good health, happiness and success, further cementing the image of a personal bond between the two authoritarian leaders. "It is difficult to overestimate the effort that you have made over many years to strengthen our comprehensive partnership and…