Victor Davis Hanson of National Review Online contends recent trends in American foreign policy point in a bad direction.

Wars often seem to come out of nowhere, as unlikely events ignite long-simmering disputes into global conflagrations.

The instigators often are weaker attackers who foolishly assume that more powerful nations wish peace at any cost, and so will not react to opportunistic aggression.

Unfortunately, our late-summer calm of 2016 has masked a lot of festering tensions that are now coming to a head — largely due to disengagement by a supposedly tired United States.

In contrast, war, unlike individual states, does not sleep.

Russia has been massing troops on its border with Ukraine. Russian president Vladimir Putin apparently believes that Europe is in utter disarray and assumes that President Obama remains most interested in apologizing to foreigners for the past evils of the United States. Putin is wagering that no tired Western power could or would stop his reabsorption of Ukraine — or the Baltic states next. Who in hip Amsterdam cares what happens to faraway Kiev?

Iran swapped American hostages for cash. An Iranian missile narrowly missed a U.S. aircraft carrier not long ago. Iranians hijacked an American boat and buzzed our warships in the Persian Gulf. There are frequent promises from Tehran to destroy either Israel, America, or both. So much for the peace dividend of the “Iran deal.”

North Korea is more than just delusional. Recent nuclear tests and missile launches toward Japan suggest that North Korean strongman Kim Jong-un actually believes that he could win a war — and thereby gain even larger concessions from the West and from his Asian neighbors.

Radical Islamists likewise seem emboldened to try more attacks on the premise that Western nations will hardly respond with overwhelming power. The past weekend brought pipe bombings in Manhattan and New Jersey as well as a mass stabbing in a Minnesota mall — and American frustration.