The announcement that President Trump’s top economic adviser, Gary D. Cohn, plans to resign after apparently losing a battle over raising tariffs ratchets up concern that the White House is turning sharply toward protectionism. The deepest fear is that the planned steel and aluminum tariffs will echo the mistake of the infamous Smoot-Hawley tariffs of 1930, which provoked a global trade war and helped fuel the Great Depression.

The alarmists are getting a bit ahead of the story, however. Periods of deglobalization — when nations begin shuttering their borders to flows of trade, money and people — tended to be slow processes, not sudden events. They started with tectonic shifts — global wars and crises — not minor import levies. And they unfolded over decades, not years. The last era of deglobalization actually began when countries turned inward after World War I, more than a decade before Smoot-Hawley and the Great Depression.