It is unclear whether Donald Trump has forgotten the precise nature of NATO or whether he ever fully grasped it in the first place.

What is clear, however, is that Trump — who ostensibly spent four years as president of the United States — has little clue of what NATO is or what NATO does. And when he spoke on the subject at a rally in South Carolina over the weekend, what he said was less a cogent discussion of foreign policy than it was gibberish — the kind of outrageous nonsense that flows without interruption from an empty and unreflective mind.

“One of the presidents of a big country stood up and said, ‘Well, sir, if we don’t pay, and we’re attacked by Russia, will you protect us?’ ” Trump said, recalling an implausible conversation with an unnamed, presumably European head of state. “‘You didn’t pay? You’re delinquent?’ ” Trump recounted responding. “ ‘No, I would not protect you. In fact, I would encourage them to do whatever the hell they want. You gotta pay. You gotta pay your bills.’”

The former president’s message was clear: If NATO members do not pay up, then he will leave them to the mercy of a continental aggressor who has already plunged one European country into death, destruction and devastation.

Except, NATO isn’t a mafia protection racket. NATO, in case anyone needs to be reminded, is a mutual defense organization, formed by treaty in 1949 as tensions between the United States and the Soviet Union hardened into conflict. “The parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all,” states Article 5 of the North Atlantic Treaty.

According to the terms of an agreement reached last year, member states will work to spend at least 2 percent of national G.D.P. on military investment.