In 2007, an Iranian-backed Shia militia known as Asaib Ahl al-Haq kidnapped and murdered five U.S. servicemen in an ambush in the Iraqi city of Karbala. At the time, the group’s deputy secretary-general was Akram al-Kaabi, a man who has since said publicly that he would gladly overthrow Iraq’s government if asked to do so by Iran’s supreme leader, Ayatollah Ali Khamenei.

Today, al-Kaabi heads a splinter faction of his original militia. Known as Harakat Hezbollah al-Nujaba, it’s now an official arm of the Iraqi security establishment, but fighting in Syria. And the United Nations has just accused it of taking part this week in the massacre of at least 82 civilians in East Aleppo, including 11 women and 13 children—a slaughter perpetrated alongside other sectarian Shiite proxies of Iran and the Russian-Iran-backed Baathist dictatorship of Bashar al-Assad.

The Syrian army as a fighting force is largely spent. Without Russian air support and the some 6,000 to 8,000 Iranian-run paramilitaries Assad now relies on to wage war for him, Aleppo would never have been recaptured.

Nor are the Iranians masking their pride in the accomplishment.

“Aleppo was liberated thanks to a coalition between Iran, Syria, Russia, and Lebanon’s Hezbollah,” Tehran’s defense minister, Seyed Yahya Rahim-Safavi, proclaimed Wednesday. “Iran is on one side of this coalition which is approaching victory and this has shown our strength. The new American president should take heed of the powers of Iran.”

That last sentence should not be read as a mere perfunctory warning to U.S. President-elect Donald Trump. It’s a statement of fact, and one that neither Trump nor his people have gotten their heads around. Trump has made it clear he wants to join the Russian side in this war, while he is adamantly opposed to the Iranian side. But in the world of real reality they are the same side.

The president-elect may have been wildly inconsistent on many of his policies throughout the 2016 campaign and transitional period, but he has been determinedly consistent on one. He is absolutely, categorically, opposed to indulging the Islamic Republic, which over the last eight years of Barack Obama’s presidency, as he sees it, has been given more or less an open invitation for conquest in the Middle East, at the embarrassing expense of U.S. interests.

Not only has Trump railed against the Obama-brokered Iran deal as “one of the worst deals ever made by any country in history” and vowed to either tear it up or renegotiate it, but all of his top national-security Cabinet picks are notable Iran hawks.

Retired Gen. James “Mad Dog” Mattis, for instance, a well-respected Marine commander and Trump’s pick for secretary of defense, told a Washington think tank last April “that among the many challenges the Mideast faces, I think Iran is actually foremost… The Iranian regime, in my mind, is the single most enduring threat to stability and peace in the Middle East."

Rep. Mike Pompeo (R-KS), an outspoken critic of the Iran deal and now Trump’s pick for CIA director, has previously called on Congress to “immediately act to stop all oil shipments out of Iran, reinstitute economic sanctions, and demand that our allies do so as well.” Pompeo also linked the Joint Comprehensive Plan of Action, as the agreement is formally known, with Iranian expansionism, noting that nothing in the protocol restricts Tehran’s “continued funding of terror activities, from Hezbollah to Hamas, from the Houthis in Yemen to the Shia militias in Iraq.”

John Bolton, Trump’s apparent selection for deputy secretary of State, agrees with Mattis that Iran is the single most destructive actor in the Middle East but goes even further: Regime change, he told the right-wing website Breitbart last month, is the “only long-term solution.”

Finally, Trump’s designated national-security adviser, the controversial Lt. Gen. Michael Flynn, is also an advocate of regime change for “Islamic republics” hostile to American interests and singles out Iran in his most recent book, Field of Fight: How We Can Win the War Against Radical Islam, as first among equals.

Flynn was fired by Obama as head of the Defense Intelligence Agency in 2014 after disputing the White House’s rather rosy portrayal of the state of global jihadism, then a hot-button talking point. Now he blames his former employer for withdrawing militarily from Iraq, thereby allowing ISIS to take over a third of the country and ceding the rest to Iran’s Quds Force, led by the hyperactive and omnipresent Qassem Soleimani. He also accuses Obama of welcoming America’s regional enemy in a “diplomatic and strategic embrace” and cites U.S. government evidence of Iran’s operational ties to various Sunni jihadi groups responsible for the deaths of Americans; not just al Qaeda and ISIS founder Abu Musab al-Zarqawi’s incipient network in Iraq, but also the Taliban in Afghanistan.

Yet Flynn is an outlier in this team of non-rivals in one crucial respect: his perceived closeness to Moscow, which has raised eyebrows in conservative circles. He was famously seated next to Vladimir Putin at the Russian state TV channel RT’s 10-year anniversary gala last year and several sources close to him, who spoke to The Daily Beast on background, attest to his view that Russia must be brought on board to help defeat the so-called caliphate. But even he acknowledges in his book what Iran’s Rahim-Safavi stated so clearly. For all intents and purposes, the Quds Force, the Party of God, and the Russians are locked in their own diplomatic and strategic embrace in the Arab world.

Herein lies the central contradiction running like Ariadne’s thread throughout Trump’s discernible foreign-policy goals. Trump has repeatedly said he wants to work with Assad and Putin, whom he admires, in defeating the ISIS minions of Abu Bakr al-Baghdadi. (Never mind that Assad and Putin can’t even keep the the Islamic State’s stormtroopers out of the ancient city of Palmyra, too busy are they fighting the non-ISIS opposition in Syria’s most populous city.) How does he purport to do that and contain and deter Iran at the same time?

Moreover, even if by some miracle Putin could be persuaded to help the United States eliminate Sunni jihadism and roll back its Iranian-controlled Shiite counterpart, would Russia’s president be able to?

The last 24 hours have proved instructive in just how messy a paradoxical strategy of appeasement and belligerence in dealing with the Assad coalition can be.

A ceasefire in Aleppo was announced Tuesday night and unraveled early Wednesday morning only to be tentatively reinstated Wednesday night. It had been brokered exclusively between Turkey and Russia and was violated, by most accounts, by the Assad regime and Iranian-led militias. On Wednesday, shelling of civilian neighborhoods resumed and the Iranian-run militias refused to allow a medical evacuation convoy into the city, demanding first that the wounded from Fuah and Kefraya, two small Shiite villages that have been targeted by rebels, also be evacuated.

Neither Damascus nor Tehran were party to the Turkish-Russian negotiations, so they set out to rewrite the terms of the resulting accord with fire and steel.

The first signs of a breakdown in the ceasefire came immediately after the accord was signed, according to Faruq Abu Bakir, the rebel official in charge of negotiations and one of the signatories along with Russian and regime representatives. He told the pro-opposition Orient TV that rebels had brought some of the wounded to a crossing into government-held Aleppo, but Shiite militia members blocked them at a checkpoint. The scene repeated itself at a second checkpoint as well.

Eighty thousand or more civilians are still stuck in the bombed-out zone with almost no food, no electricity, and no heat, and there are an enormous number of wounded waiting to be evacuated—and others still pinned under rubble. A second ceasefire was announced Wednesday night, but there’s hardly a guarantee that this one will prove any different from the first.

Trump’s Cabinet-to-be is not necessarily wrong in its assessment of Iran’s lengthened and deleterious reach in the region, although curiously it hasn’t used the Syria catastrophe to make this point lately.

Obama officials recently came clean in stating their singular quest for a nuclear agreement with Tehran was a major reason for their reluctance to get more involved in the Syrian civil war on the side of the opposition. The fall of Aleppo is a direct result of that choice. Respecting “Iranian equities” in the Levant, as Obama himself has phrased it, was integral to his long sought and long elusive political settlement of the five-and-a-half-year-old conflict, which involved not picking a fight with Qassem Soleimani and agreeing to any number of high-fiving boondoggles between John Kerry and Sergei Lavrov in Switzerland.

"Iranian equities" are shooting women and children dead in the street in Aleppo while U.S. Central Command operates as their de facto ally in the ongoing war against ISIS in Iraq.

The irony of a Trump foreign policy may well be that for all the candidate’s bravado and his condemnation of Obama’s outreach to America’s Iranian enemies, his own confused approach to geopolitics may end up with him doing exactly what his predecessor tried. And failing, too.

—Roy Gutman in Istanbul also contributed to this article