How to recognize a trade war

Calm before the storm. West Lake in Hangzhou, China. Photo: Johannes Eisele / AFP / Getty

With billions of dollars in tariffs threatened on both sides, the U.S. and China look like warring nations. But experienced trade hands tell us these are only appearances — it's the chest-thumping brinksmanship stage of negotiations, they say.

Okay, but if so, when will we know we are watching war?