With the threat of a trade war looming over the global economy, it may feel like the world has been force-fed another one of U.S. President Donald Trump's signature cocktails -- shaken on the rocks, with equal parts tweets and tariffs, and a twist of terror. But if you want to shake off that foggy feeling and get a clearer vision of what will come to pass, focus on the line between a president's tactics, no matter how unorthodox, and the country's grand strategy. Great power rivalry is what gave rise to the global trading order in the 20th century; the return of peer competition will shake, but not necessarily break, that foundation in the 21st....