President Trump, after warning three days ago that Iran would pay "a very BIG PRICE," authorized a drone strike at Baghdad International Airport that killed Iran's top general and second most powerful official, Qasem Soleimani.

• From the Pentagon's statement: "At the direction of the President, the U.S. military has taken decisive defensive action to protect U.S. personnel abroad by killing Qasem Soleimani, the head of the Islamic Revolutionary Guard Corps-Quds Force, a U.S.-designated Foreign Terrorist Organization."
• The strike also killed Abu Mahdi al-Muhandis, the deputy commander of the Popular Mobilization Forces, a group of Iranian-backed militias in Iraq.

Why it matters: Soleimani had cost hundreds of American lives and was among the Middle East's most feared powers. But Iran seems certain to respond, potentially further destabilizing the world's most volatile region.

• "In killing General Soleimani," the N.Y. Times reports, "Trump took an action that Presidents George W. Bush and Barack Obama had rejected, fearing it would lead to war between the United States and Iran."

Behind the scenes: A source in close contact with Trump administration senior national security officials tells Axios' Jonathan Swan that one scenario they are especially concerned about — and have been prepared for — is Iran launching cyberattacks.

• That's the most likely way that Iran could retaliate stateside.

The big picture: The president who wanted to bring home the troops is now engaged in the most intense conflict with Iran in recent history.

• So much has changed — and so fast.
• A few months ago, Trump was musing about bringing U.S. troops home from the Middle East, and to let others fight it out in the sand.
• Now, he’s adding forces, and they’re necessarily on a war footing.

The bottom line: Modern wars are fought mostly with the most expensive, most difficult to recruit, train and retain: special forces. 

President Trump has to prepare for an extreme backlash from Iran — and likely intensified attacks on U.S. forces in the Middle East, and anywhere else within Iran’s planning reach.

It also means possible retaliation against U.S. allies, especially Israel, writes Axios contributor Barak Ravid.

• Prime Minister Benjamin Netanyahu cut short a trip to Greece to return to Israel to monitor the situation.
• It is still unclear if the U.S. gave Israel any heads up before the strike on Soleimani.
• Israeli officials tell Ravid that Israel doesn’t know if and how Iran is going to retaliate — but, right now, the decision is to keep a low profile and not get involved in the ongoing tensions in Iraq.

CFR President Richard Haass tweets: "Make no mistake: any war with Iran will not look like the 1990 Gulf war or the 2003 Iraq wars."

• "It will be fought throughout the region w a wide range of tools vs a wide range of civilian, economic, & military targets. The region (and possibly the world) will be the battlefield."

President Trump tweeted this wordless image last night, about 15 minutes before the Pentagon statement confirming the strike:

To catch up quickly on why Qasem Soleimani was one of the most significant figures in the Middle East, here are five quick points from a 2013 profile by Dexter Filkins in The New Yorker, "The Shadow Commander":

• "Suleimani ... has sought to reshape the Middle East in Iran's favor, working as a power broker and as a military force: assassinating rivals, arming allies, and, for most of a decade, directing a network of militant groups that killed hundreds of Americans in Iraq."
• "His power comes mostly from his close relationship with [Iran's ruler, Ayatollah Ali Khamenei] ... The Supreme Leader, who usually reserves his highest praise for fallen soldiers, has referred to Suleimani as 'a living martyr of the revolution.' Suleimani is a hard-line supporter of Iran’s authoritarian system."

"In 2004, the Quds Force [that he led] began flooding Iraq with lethal roadside bombs that ... began to wreak havoc on American troops, accounting for nearly twenty per cent of combat deaths," Filkins continues.

• "[H]e has remained mostly invisible to the outside world, even as he runs agents and directs operations. 'Suleimani is the single most powerful operative in the Middle East today,' John Maguire, a former C.I.A. officer in Iraq, told me."
• In a report to the White House, Gen. David Petraeus, then commander of coalition forces in Iraq, wrote that Soleimani was "truly evil."

Keep reading (paywall).

Speaker Pelosi said in a statement that the Iraq strike "was taken without the consultation of the Congress," and "risks provoking further dangerous escalation of violence":

• "The full Congress must be immediately briefed on this serious situation and on the next steps under consideration by the Administration, including the significant escalation of the deployment of additional troops to the region."

2020 Dems condemn: Joe Biden said President Trump "tossed a stick of dynamite into a tinderbox" with the targeted killing of Iran's top general, and said it could leave the U.S. "on the brink of a major conflict across the Middle East," AP reports.

• Bernie Sanders said: "Trump's dangerous escalation brings us closer to another disastrous war in the Middle East that could cost countless lives and trillions more dollars."
• Elizabeth Warren called Qasem Soleimani "a murderer, responsible for the deaths of thousands, including hundreds of Americans." But she said Trump's "reckless move escalates the situation with Iran and increases the likelihood of more deaths and new Middle East conflict."
• Andrew Yang tweeted: "War with Iran is the last thing we need and is not the will of the American people. We should be acting to deescalate tensions and protect our people in the region."

Auto companies, counterintuitively, are trying to get people to give up their cars — by making shared transportation more appealing with vehicles that recognize you, anticipate your needs and customize your ride, Axios' Joann Muller writes.

• Why it matters: Ride-hailing apps are making urban congestion steadily worse. In San Francisco, people spent 62% more time sitting in traffic in 2016 than in 2010. Uber and Lyft admitted they're part of the problem.

The most important carrot could be convenience: In New York, bus ridership soared after a car ban on 14th Street cleared the way for buses, shortening travel time by 30%.

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Bernie Sanders' $35 million fourth-quarter fundraising, which easily tops 2020 Democrats, is a timely reminder that the socialist senator from Vermont is the single most consistently popular and viable Democrat of the past half-decade. 

• Why it matters: The media rarely treats Sanders, 78, with the seriousness warranted by his sustained popularity and fundraising.
• Like in 2016, Sanders has a legit shot to win the nomination — and an unshakable base to brace him. 

The data: 

• Since 2015, Sanders has raised more from small contributions (under $200) than any other Democrat, highlighting his grassroots support.
• In both the 2016 and 2020 cycles, about 57% of his total fundraising came from small contributions. Joe Biden's share of fundraising from small contributions so far is only 35%.
• Sanders' campaign says it took in 1.8 million donations during the fourth quarter — an average of $18.53.

The bottom line: Despite his age, and even after a heart attack and the insertion of stents this past fall, Sanders is surging again.

• He is now second in national polling, behind the equally resilient Biden.

Between the lines: "His anti-establishment message hasn’t changed for 50 years, and it resonates with working-class voters and young people who agree the system is corrupt," the N.Y. Times wrote from Iowa last week.

• "Sanders's revival has reshuffled the Democratic primary race, providing a counterweight to the shift toward centrism in recent months that has elevated Mayor Pete Buttigieg."

Apple's new streaming service is only beginning to take shape, but already the tech giant has signaled that it's willing to spend big to lure Hollywood's top talent to be a part of it, writes Axios media trends expert Sara Fischer.

• Driving the news: Former HBO boss Richard Plepler has secured a five-year exclusive deal with Apple to produce feature films, documentaries and original series for Apple TV+, his spokesperson confirmed to Axios.

Alex Trebek, 79, says he's already rehearsed what he's going to say to the audience on his final "Jeopardy!" — whenever that may be.

• Trebek, host of the iconic game show since 1984, announced last March that he'd been diagnosed with stage 4 pancreatic cancer but would continue working, AP writes.

In an interview with ABC's Michael Strahan broadcast in primetime last night, Trebek said he'll ask the director to leave him 30 seconds at the end of his last taping:

I will say my goodbyes and I will tell people, "Don't ask me who's going to replace me, because I have no say whatsoever. But I'm sure that if you give them the same love and attention and respect that you have shown me ... then they will be a success and the show will continue being a success ... And until we meet again, God bless you and goodbye."