LIBERTARIAN PRESIDENTIAL nominee Gary Johnson embarrassed himself Thursday when he was asked about the epicenter of Syria’s civil war and responded, “What is Aleppo?” The moment, on an MSNBC morning program, deserves to become iconic because it encapsulates why Mr. Johnson is not fit to be president. His disregard for U.S. foreign policy and strategic interests is so profound that he did not recognize a reference to Syria’s largest city, which, for several years, has been the site of intense fighting, massive war crimes and an ongoing humanitarian crisis that has, with its tidal wave of refugees, rocked prime U.S. allies in Europe.

But let’s be fair to Mr. Johnson: In the context of the 2016 presidential campaign, he’s far from winning the cluelessness contest. Following his gaffe, the former New Mexico governor offered a relatively cogent summary of U.S. support for various Syrian factions. Later, he apologized, saying that he thought “Aleppo” was an acronym. “I feel horrible,” he said to Bloomberg Politics. “I have to get smarter, and that’s just part of the process.”

It’s refreshing, at least, to hear a national candidate acknowledge error and vow to do better. Contrast that with Donald Trump, who in a televised national security forum Wednesday offered a staggering array of ignorant and mendacious assertions — and acknowledged no regrets about any of them. In addition to repeating his false claims to having opposed the U.S. interventions in Iraq and Libya, Mr. Trump defended a tweet saying that military sexual assault was the result of men and women serving together, and he suggested the solution was to “set up a court system within the military” because “right now, the court system practically doesn’t exist.” Does he really mean to replace the U.S. military justice system?

At least that would be easier than Mr. Trump’s plan to “take the oil” of Iraq: “Just we would leave a certain group behind, and you would take various sections where they have the oil.” The jaw-dropping imbecility of this idea surely would make even Mr. Johnson wince.

Most troubling of all was Mr. Trump’s renewed endorsement for Vladi­mir Putin, in spite of the mounting evidence that the Russian government is attempting to directly interfere in the U.S. election campaign. Confronted with a litany of Mr. Putin’s offenses, including the military actions in Ukraine and Syria and the computer hack of the Democratic National Committee, Mr. Trump responded, “Do you want me to start naming some of the things that President Obama does at the same time?” — as if there were equivalent U.S. actions.

Appearing on MSNBC's "Morning Joe,” Libertarian Party presidential candidate Gary Johnson was asked what he would do about Aleppo if he were elected president. Johnson replied, “What is Aleppo?” Here's what he needs to know. (Jason Aldag/The Washington Post)

“He is really very much of a leader,” Mr. Trump said of a man who has overseen the murder of his domestic political opponents and critical journalists, the rigging of elections, a global campaign of disinformation and a foreign policy whose first aim is to increase Russian influence at U.S. expense.

Mr. Johnson may not know what Aleppo is. But in the contest between the United States and an autocratic and increasingly belligerent Russia, Mr. Trump appears not to be sure which side he is on.