When he set out to extract concessions from China and other countries, President Donald Trump assured Americans that trade wars are good, and easy to win. He regarded previous presidents as easy marks for devious foreign governments, and he thought his tough tactics would force those rivals to back down.
But after two years of negotiations with Beijing, victory has proved elusive. What was mostly an exercise in posturing and demands is turning into a full-fledged battle that threatens to produce mass casualties.
On Thursday, the president abruptly announced that he would slap…
