U.S. President Donald Trump is not the first commander-in-chief to cut and run from the Middle East, in defiance of his own defence secretary’s advice, just to fulfill an election promise.

In 2011, president Barack Obama proceeded with the withdrawal of all U.S. combat troops from Iraq despite the opposition of then-defence secretary Leon Panetta and his own military advisers. While Mr. Obama insisted the 2011 deadline had been set out in an agreement signed in 2008 by George W. Bush’s administration and the Iraqi government, Mr. Panetta and his generals warned Iraq was not ready to stand on its own.

“Now that the deadline was upon us, however, it was clear to me – and many others – that withdrawing all our forces would endanger the fragile stability then barely holding Iraq together,” Mr. Panetta wrote in his 2014 memoirs.

Mr. Obama had his own reasons for spurning Mr. Panetta’s advice. His opposition to Mr. Bush’s 2003 invasion of Iraq had helped him win the 2008 Democratic presidential nomination against then-senator Hillary Clinton, who had voted for the war. Mr. Obama had campaigned on extricating the United States from “bad wars” and vowed to end the Iraq mission, and was preparing for his own re-election campaign.

But without a U.S. military presence to ensure Iraq’s stability, the Shiite-led government of then-prime minister Nouri al-Maliki presided over a resurgence of sectarian violence that facilitated the emergence of the Sunni-led Islamic State. By 2014, IS had driven Iraqi forces out of several cities and moved across the border into Syria, which was engrossed in its own civil war.

Mr. Obama’s decision not to intervene in Syria then – despite having threatened to do so if President Bashar al-Assad used chemical weapons, which he did – had much broader consequences than Mr. Trump’s move to withdraw U.S. troops is likely to cause now.

Had Mr. Obama ordered U.S. air strikes, he might have driven Mr. al-Assad from power and wiped out IS. But, he was rightly concerned about what might happen following Mr. al-Assad’s demise, having presided over the disaster that unfolded in Libya after the United States and its NATO allies, including Canada, intervened to overthrow Moammar Gadhafi in early 2011.

By 2015, Russian President Vladimir Putin and Iranian militias backed by Tehran’s Revolutionary Guard had intervened to prop up Mr. al-Assad. Hundreds of thousands of civilians died; millions more fled the country as refugees.

Mr. Obama did eventually send U.S. troops to aid in the fight against IS, but the move was too little, and it came too late for the United States to exercise anything resembling influence over Syria’s fate. Hence, Mr. Trump’s withdrawal of the 2,000 U.S. troops in Syria will do nothing to alter the balance of power on the ground, where Russia and Iran have been running the show.

That does not mean Mr. Trump’s seemingly impulsive decision-making – as evidenced by his move to oust Defence Secretary General James Mattis on Jan. 1, two months before his resignation was originally meant to take effect – is not a source of concern or instability. But the withdrawal of a marginal U.S. force from a country that has already been lost to adversaries of the United States is probably not much of a game changer in itself, unless it is a signal of a broader U.S. retreat into isolationism and the overall abandonment of the Middle East.

Yet, Mr. Trump himself sought to dispel that impression during his surprise Christmas visit to U.S. troops that had been stationed in Iraq since 2015, saying: “If we see something happening with [IS] that we don’t like, we can hit them so fast and so hard they really won’t know what the hell happened.”

There is a real danger that Mr. Mattis’s departure and the Syria pull-out mark the beginning of a series of decisions by Mr. Trump that truly destabilizes the global order. But it would be premature to make that conclusion now. Mr. Trump may be more strategic than he gets credit for if he gets U.S. allies, including Canada, to take seriously his threats of a broader withdrawal of the thousands of U.S. forces stationed around the globe. Until now, they haven’t.

After all, it’s been more than 18 months since Foreign Affairs Minister Chrystia Freeland delivered a seminal House of Commons speech in which she promised Canada would “step up” to strengthen the postwar multilateral order as “our friend and ally has come to question the very worth of its mantle of global leadership.” Stepping up was supposed to involve making “the necessary investments in our military, to not only redress years of neglect and underfunding, but also to place the Canadian Armed Forces on a new footing.” Yet, Mr. Trump is still waiting for Canada and other NATO allies to make good on their defence-spending commitments.

No one should act surprised if he shows signs of getting impatient.