And with the strikes, Americans were confronted with a reality they were led to believe they'd never see: President Trump using elective military action for humanitarian purposes, and doing so without congressional approval.

During the campaign and even before it, Trump forcefully derided U.S. military involvement in the Middle East, repeatedly saying the war in Iraq was a disastrous mistake and that he would focus on "America first.” And he wasn't afraid to appear cold in the face of the refugee crisis and suffering in Syria; it was a problem for the Middle East to solve, and no refugees would be admitted into the United States for fear of admitting terrorists. He even suggested military action could lead to another world war.

“Now wants to start a shooting war in Syria in conflict with a nuclear armed Russia that could very well lead to World War III,” Trump said just days before the 2016 election.

Trump also in 2013 derided the specific idea of retaliating against the Syrian government for using chemical weapons, repeatedly urging President Barack Obama not to involve the United States in the civil war, despite Obama's “red line” policy. Trump also said that, if Obama did decide to strike, he should seek Congress's approval.

The events of Thursday night run completely counter to all of that. Trump is reported to have been personally affected by the scenes of suffering and the information he has learned now that he's president — “Even beautiful babies were cruelly murdered in this very barbaric attack,” he said late Thursday night in brief remarks, adding: “No child of God should ever suffer such horror” — but the barbarism and horror were there in 2013. Yet Trump took a firm line against intervention for years.

It may seem trivial to focus on Trump's past words in the light of the suffering in Syria and the realities of actually being president. But the fact is that the United States elected a man who promised to use force in a very circumspect manner and spoke unequivocally about it.

And it's likely that the noninterventionist promises Trump made during the campaign helped him by allaying some of the greatest fears about making him president and commander in chief. Arguably his biggest liability was that people — even many supporters — believed he lacked the proper temperament to be president. The prospect of the hotheaded, itchy-Twitter-fingered reality TV star having access to the nuclear codes was an attack ad that practically wrote itself. And there were plenty who argued that his noninterventionist talk was just that -- talk -- and that he couldn't be trusted to deal with international conflicts.

But Trump's promises to stay out of the Middle East and focus on the homeland mitigated that line of attack. Voters were led to believe his foreign policy wouldn't be on the same hair trigger that everything else about him seemed to be, and it gave them license to instead focus on what a businessman president could do for the economy.

Yet here we are. Less than three months into his presidency, Trump has now responded to a not-unprecedented set of circumstances in Syria with an unprecedented degree of force and provocation.

Reporter Dan Lamothe explains why the president authorized the launch of 59 Tomahawk missiles at a Syrian airfield and what it means for the fight against ISIS. (Sarah Parnass, Julio Negron/The Washington Post)