Go one step beyond that, and countries are going to begin blockading shipping and closing borders entirely. Finally, there is the danger of war as the only recourse that some leaders will decide is needed to set matters straight again.
Think of Chinese support for North Korea: Pyongyang relies on Beijing for virtually all its oil and a large percentage of its food, among many other items. If the US fails in its dialogue with North Korea over denuclearisation and the danger of war again hovers over the Korean peninsula, China would surely side with North Korea, as it did in the Korean war.
The stand-off with China extends all round the rim of Asia, down to the South China Sea and on to the Indian Ocean and the Arabian Sea, and beyond.
Korea’s trade surplus with the US last year was US$23.1 billion, down from a high of US$28.3 billion in 2015 but still considerably more than US trade officials would like.
Japan, whose surplus with the US last year reached US$68.8 billion, down from a peak of US$76.4 billion in 2012 but still far too high.
With numbers like these, it’s easy to see why Trump is talking so tough about the trade deficit while America’s trading partners are outraged by moves to cut it.
The fear, however, is that these nasty battles could eventually explode into armed conflict in which hundreds of millions, maybe billions, would perish. Policymakers and negotiators have to keep this risk at the top of their concerns as they confront one another in a global trade war that could someday erupt into the third world war.