Donald Trump's missile barrage on Syria  -- the first major military gambit of his presidency -- revealed a leader fueled by instinct and emotion, and one willing to shake up strategy in an instant.

Early Tuesday, horrifying details started trickling into the White House Situation Room -- a secure suite in the bowels of the West Wing that serves as the presidency's eyes and ears on the globe.

The initial picture was sketchy, but US military and intelligence came to believe that 5,750 miles (9,250 kilometers) away in Khan Sheikhun, Syria, a fixed-wing aircraft from Bashar al-Assad's air force unleashed a deadly harvest of sarin nerve agent on villagers who oppose his regime.

At around 10:30 am Washington time, US intelligence officers took their news to Trump as part of his top-secret daily briefing.

At the same time, news agencies with reporters on the ground, like AFP, began showing the horrifying reality of those clinical facts: heart-wrenching images of convulsing toddlers, empty-eyed men and women, and panicked efforts to hose the deadly agent off those still alive.

According to White House officials, this most visually focused of presidents -- a man whose life has been defined by the power of image and television -- had an immediate and visceral response to the images, asking for more information and options. 

"It crossed a lot of lines for me," Trump said in a stunningly frank Rose Garden press conference the next day.

"When you kill innocent children, innocent babies -- babies, little babies -- with a chemical gas that is so lethal -- people were shocked to hear what gas it was -- that crosses many, many lines, beyond a red line."

- 'I now have responsibility' -

Before that moment, Trump had railed against his predecessors' military adventurism in the Middle East, arguing it was time to move on from wars in Iraq and Afghanistan and put "America first."

Trump had variously argued that Assad's brutal actions were not really America's problem and that the Syrian dictator -- and his Russian backers -- could even be allies in fighting the Islamic State group. 

This was a complete U-turn. Now Trump wanted a response. 

"I now have responsibility, and I will have that responsibility and carry it very proudly," he said. 

Within 24 hours, a speed that shocked allies and even some inside the administration, military and national security officials had presented the president with multiple options.

At around 2:00 pm Thursday, Trump ordered the military to launch a barrage of 59 Tomahawk missiles at the Shayrat airfield from US Navy ships in the Mediterranean.

It was an overwhelming display of power, but less risky than flying sorties in an area covered by Russia's S-400 missile defense system and less escalatory than striking Syrian military headquarters or civilian government targets. 

Trump, ever the CEO, was so comfortable with his decision that hours before the attack, he was cracking jokes with Chinese President Xi Jinping, who he was hosting at his Florida resort.From the relaxed atmosphere of Mar-a-Lago, there were no signs that Trump had ordered an attack that could mark his presidency and dramatically alter the geopolitical dynamic of the Middle East. 

- Uncertain aftermath -

Top administration officials painted the decision as a display of presidential strength and resolve. The message? There was a new sheriff in town.

Under Trump, there would be none of the ignored red lines or months-long deliberations that characterized the administration of Barack Obama.

"It's decisive, and I have no doubt that he wanted that contrast with President Obama's indecisiveness on Syria," Larry Sabato, director of the Center for Politics at the University of Virginia, told AFP.

"But part of it is also worrisome. This is a president who doesn't know what he doesn't know. We've all seen it."

Amid a myriad of questions about long-term strategy and the legality of the strike, top administration officials have struggled to explain the rationale beyond Trump's reaction.

Secretary of State Rex Tillerson and National Security Advisor HR McMaster painted the strike both as a specific response to a specific breach of chemical weapons norms and as a warning to the world at large that Trump and America should not be messed with.

By dawn on Friday, capitals from London to Tokyo, from Tehran to Pyongyang were trying to figure out whether the strike was one-and-done or the opening salvo of a new Trump doctrine -- with most leaning toward the former.

Even White House officials privately admitted that while Trump means business and the Syria strike may be repeated, it is not obviously transferable to other crises.

Striking North Korea, one official admitted on condition of anonymity, would be a much more fraught piece of business.

The US is now girding for an asymmetrical response from Assad or his backers in Tehran via Hezbollah militiamen, but the White House admits an attack on Pyongyang would almost certainly prompt a much more serious direct response targeting allies in South Korea or Japan.

What is clear from the strike is that Trump trusts and acts on his own instincts.

"I'm a very instinctual person, but my instinct turns out to be right," he recently remarked.

Sabato however said "there's just one problem" with that approach.

"He's a human being and his instincts are just as flawed as anyone else's," he said.

source: AFP