Washington (CNN) President Donald Trump flipped years of international policy on its head in a 12-hour span on Thursday by punishing American allies for producing steel and aluminum and rewarding an American enemy with a presidential meeting.

The decisions -- first to impose a 25% tariff on steel and 10% tariff on aluminum over the cries of American allies and second to agree to a meeting with North Korean leader Kim Jong Un without detailed preconditions -- was quintessential Trump. White House aides, even those who were left in the dark on much of it, were nonplussed about the fact that the President was breaking the mold.

Their collective response: This is what he promised to do.

But Thursday represented more than just a campaign promise fulfilled. It signified a stark break from years of American foreign policy that has looked to reward friends and punish enemies, one that had experts worried the United States was taking too dramatic a step on trade and too risky a step on foreign policy.

Trade wars

Trump's first decision -- to impose a 25% tariff on steel imports and a 10% tariff on aluminum -- rankled American allies, leading them to promise a punitive response on all American products like bourbon, jeans and motorcycles.

While the action was heralded by steel unions and Trump's base of voters -- even the Democratic-leaning AFL-CIO union group heralded the move as a way to punish international cheaters -- the decision is expected to raise prices on companies that use steel products and divided an already deeply split White House.

But, as a subtle warning to the President, 11 of the nations allies got together on the same day that he imposed tariffs to sign the Trans-Pacific Partnership, a sweeping trade agreement that Trump withdrew from last year

The agreement brings Mexico, Canada, Japan and a host of other nations -- all longtime American allies -- closer together, with the United States on the outside looking in.

North Korea

The more surprising choice came when South Korean negotiators, after briefing the President, announced on the driveway of the White House that North Korean leader Kim Jong Un extended an invitation to meet with Trump, which the President quickly accepted.

The possible meeting jolted Washington, with even longtime North Korea experts befuddled by how Trump got from calling Trump "short and fat" to meeting with him in mere months. These experts had a primary warning for Trump, too: Do not reward Kim, a brutal dictator who has consolidated power through murder, with a presidential meeting.

And on Friday, hours after the announcement, significant questions remained about what exactly Trump had agreed to.

"Let's be very clear, the United States has made zero concessions, but North Korea has made some promises," Sanders told reporters. "And again, this meeting won't take place without concrete actions that match the promises that have been made by North Korea."

White House officials later said that nothing had changed in the United States' stance towards the Kim invite, but the uncertainty about the meeting -- even before any details had been hammered out -- signaled how delicate a meeting between Trump and Kim would be.

North Korea expert Gordon Chang reflected on the "extraordinary week" that proved, he said, that Trump is flatly a "willful president."

"There are always a million reasons not to do something," Chang said, "and what Trump has said to everybody with the tariff decision, with the impulsive decision to talk to Kim Jong Un, is I don't care, I am following my instincts.' "

Unprecedented presidency

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The week was more proof that Trump's maxim during the 2016 campaign -- that he would be a different kind of president -- was still operable.

But, as has been the case with Trump's first year in office, the President's pre-campaign rhetoric is often at odds with his administration's actions. Case in point: Trump's decision to meet with Kim put Trump in a similar position to the man he loves to needle, Barack Obama.

Republicans decried the former President for saying during a CNN debate in 2007 that he would be willing to meet with leaders of Iran, Syria, Venezuela, Cuba and North Korea without preconditions. Even as Republican claim Trump has already secured conditions to meet with Kim, Trump is now in a position where he is counting on a unreliable country to make good on their pledges.

Obama never ended up meeting with Kim -- no sitting US president has ever met with the head of the rogue nation -- but he did meet with Cuban President Raul Castro in 2016, an encounter that Trump faulted as a waste of time, even if the gulf that separates communist Cuba and the democratic United States has been a foreign policy issue for decades.