"If Greenland is annexed by the United States, China must take Taiwan," wrote Wang Jiangyu, a professor of law at City University of Hong Kong, on microblog site Weibo. One commentator on a blog run by Chinese search engine Baidu said that if Trump does move on Greenland, China should "seize the opportunity to take back Taiwan".

Nicholas Burns, the U.S. ambassador to China, also said he was leaving his post with deep concerns about the future of relations with China.

Some of Trumps threats to take over Greenland, Canada, and the Panama Canal are based on actual U.S. strategic goals. Others are just idiotic.