Trump’s deployment of more than 5,000 American troops to the southern border – a mission that cannot in good conscience be called quixotic only because at least Don Quixote actually believed the windmills at which he was tilting were real monsters – will cost American taxpayers at least $72 million, the Pentagon said on Tuesday.

The real number is higher still, because it includes Trump’s activation earlier in the year of the National Guard to the border, which cost a further $138 million. That means that it is now possible to put a price-tag on one of the most bare-faced and cynical election stunts in American history: $210 million.

Trump only talked about the so-called “migrant caravan” – which he framed as an invading army, playing to the fears of White Nationalists by describing them almost lasciviously as “young strong men” many of whom could be “Middle Eastern” – in order to activate his base in border states such as Texas.

The so-called caravan is an annual event, and is actually a group of asylum-seekers from parts of Central America whose lives are threatened and who are traveling together for reasons of safety. The ultimate irony, of course, is that the violence from which many of them are fleeing is the result of decades of American foreign policy, especially the drug war, which has turned much of the region over to the control of powerful drug cartels.

Any sense that Trump really believed that the caravan posed a real threat has been entirely stamped out by the fact that, now that the election is over and it has served its purpose as a bogeyman, he has almost stopped mentioning it except when pressed by the media. Certainly he would not admit the key point, which is that the caravan happens each year, and they intend to apply for asylum at the US border – a totally legal process – rather than try to enter illegally.

Sure, presidents have used military action for electioneering purposes before. It is one of the tenets of democracy that military deployments in the short term shore up polling and allow a leader previously perceived as weak to be perceived as strong.

No, of course it was just for election purposes, which meant that his deployment of US soldiers to the border at huge taxpayer expense was just an election stunt, the action of a would-be strongman trying to flex his muscles against an invisible and unarmed foe.

Trump’s attitude toward the border led in late November to one of the most deeply troubling moments of his whole administration, when American border patrol forces fired tear-gas into a crowd of migrants including women and small children in Tijuana, on the Mexican side of the border with California.

This awful scene led to administration surrogates tying themselves in knots trying once more to defend the indefensible, with one even saying that the pepper-spray used was so safe that “you can actually put it on your nachos and eat it.”

The whole debacle was already indefensible, but it is even more so now that we know that the whole grand theatrical event is costing US taxpayers such a colossal amount of money.