Ted Carpenter, a senior fellow on defense and foreign policy studies at Cato Institute, Washington.

The G20 sent a strong message supporting open trade and warning of the dangers of protectionism. That was a major theme of President Xi Jinping's speech, largely a response to worrisome trends in the United States.

In addition to countering the problem of economic protectionism, the G20 addressed the growing problem of destabilizing wars and the massive refugee problems they are creating. Once again, China was a voice for greater restraint.

Unfortunately, there were reminders of disruptions to global unity. Despite apparently constructive talks on the sidelines, Russia and the US could not reach an agreement on new measures to resolve the Syria conflict.