Mr. Trump’s fondness for tanks is part of the insidious nostalgia that undergirds his entire “Make America Great Again” ideology. It evokes a “simpler” time, when Gen. George Patton’s tanks saved the world from the Nazis, when winning the Cold War meant winning the arms race — a time before the Vietnam War forced the country to question the morality and wisdom of its “defense” industry, before an increasingly skeptical media revealed the truth about the My Lai massacre, the Iran-contra affair and torture at Abu Ghraib. Mr. Trump has promised his followers that he can take them back to that time — and they seem ready to believe him.

Mr. Trump is a wannabe strongman, and no doubt he sees in the tank what all strongmen see in tanks: a weapon to be used against his enemies, foreign or domestic. Though tanks over the past half century have been used only rarely in their strategic combat role, they have been used often to repress popular uprisings — a tool of practical and psychological warfare against unarmed civilians from the Eastern Bloc of the Soviet Union to Tiananmen Square. By displaying tanks in our nation’s capital, Mr. Trump signals that he is willing to use the military for personal political purposes, as he did in May when the White House asked the Navy to hide the U.S.S. John McCain during his trip to Japan.