Few tears will be shed if the brutal regime of the Islamic Republic of Iran is consigned to the dustbin of history. But President Trump’s call for the Iranian people to “keep protesting” and “take over your institutions” because “HELP IS ON ITS WAY” is doubly dangerous.

If Trump’s promise of help is kept, the President could be leading the United States down the path of yet another adventure in regime change in which the cost in American blood and treasure is uncertain and the ultimate outcome in Iran and the region is unpredictable. But if he breaks his promise, Trump may have condemned thousands of Iranians to imprisonment, death or both.

We know this because America and the world have seen this movie produced by presidents of both parties over the past 35 years. The bodies of the hundreds of thousands of dead Iraqis and Syrians tell the tale.

During the First Gulf War, the United States and its coalition allies ejected Saddam Hussein’s forces from Kuwait and destroyed the Iraqi military. But President George H.W. Bush ultimately halted the allied invasion short of Baghdad and rejected the toppling of Saddam as a war aim. Nevertheless, on February 15, 1991, President Bush urged the Iraqi military and the Iraqi people to rise up and “take matters into their own hands.”

But there's another way for the bloodshed to stop. And that is for the Iraqi military and the Iraqi people to take matters into their own hands -- to force Saddam Hussein, the dictator, to step aside, and to comply with the United Nations resolutions and then rejoin the family of peace-loving nations.

Bush reiterated that message on March 2, 1991:

In my own view I've always said that it would be, that the Iraqi people should put him aside, and that would facilitate the resolution of all these problems that exist.

The Iraqi people—especially the Shiites in the south and the Kurds in the north—answered President Bush’s clarion call. They did take matters and rise up against Saddam. But the American military support they expected never materialized. Making matters worse, U.S. commander General Norman Schwarzkopf was “suckered” (his words) into allowing the Iraqi military to continue to fly its helicopters after the cease fire. Without American help, as the National Interest recalled, the uprising was crushed and 100,000 Shia and Kurds killed by Saddam’s forces:

In the end, Saddam Hussein’s regime, using only helicopters, long-range artillery, and armored ground forces, brutally counterattacked the uprising, killing 30,000-60,000 Shias in the south, and some 20,000 Kurds in the north. Though the United States had enormous military capabilities in the Persian Gulf, the Bush administration provided no assistance to the uprisings, fearing, variously, the “Lebanonization of Iraq,” Iranian-backed Shias assuming power in Baghdad and more U.S. soldiers dying in “another Vietnam,” as then-Secretary of State James Baker described it. The Bush administration also actively restrained the uprisings by refusing to provide captured Iraqi weapons or munitions stockpiles to the insurgents, but rather chose to destroy them, return them to the Iraqis, or transfer them to the Mujahideen in Afghanistan. By early April 1991, Hussein’s regime had completely crushed both Shia and Kurdish resistances. By mid-April, American, British, and French planes began enforcing a comprehensive no-fly-zone above the 36th parallel in northern Iraq, which they would sustain for the next dozen years.

For the next dozen years, that is, until President George W. Bush used the canards of Saddam’s mythical weapons of mass destruction and bogus ties to Al Qaeda to pursue regime change in deadly earnest. And as you’ll recall, despite Vice President Dick Cheney’s boasts to the contrary, we were not greeted as liberators.

But Bush 41 isn’t the only President in recent memory whose broken promises--real or perceived--delivered brave opposition protesters to the slaughter. In his own way, President Barack Obama discovered the road to hell is paved with good intentions.

In 2011, the Arab Spring witnessed anti-regime and pro-democracy protests sweep across North Africa and the Persian Gulf. What started in Tunisia lit a match that set fire to Libya, Egypt, Yemen, Syria and Bahrain. But as Libya strongman Muammar Qaddafi prepared to massacre his own people in the streets of Benghazi and other cities, the United States and its NATO allies intervened to prevent the slaughter. On March 18, 2011, President Obama spoke to the American people about why the U.S. would support a British-French operation to halt Qaddafi’s campaign of violent oppression:

Now, here is why this matters to us. Left unchecked, we have every reason to believe that Qaddafi would commit atrocities against his people. Many thousands could die. A humanitarian crisis would ensue. The entire region could be destabilized, endangering many of our allies and partners. The calls of the Libyan people for help would go unanswered. The democratic values that we stand for would be overrun. Moreover, the words of the international community would be rendered hollow.

Obama repeatedly emphasized that his action in Libya did not herald a new American doctrine of humanitarian intervention in the region. As he put it a week later on March 26, 2011:

As Commander in Chief, I face no greater decision than sending our military men and women into harm’s way. And the United States should not—and cannot—intervene every time there’s a crisis somewhere in the world.

But I firmly believe that when innocent people are being brutalized; when someone like Qaddafi threatens a bloodbath that could destabilize an entire region; and when the international community is prepared to come together to save many thousands of lives—then it’s in our national interest to act. And it’s our responsibility. This is one of those times.

But the blowback from Obama’s “Libya One-Off” ultimately double. The humanitarian calamity in Libya was averted, with Qaddafi deposed and killed. But with no plan in place for the day after, Libya degenerated into a fragmented and extremely fragile state with rival militias jockeying for power and resources. There have been no elections since 2014 while the 2020 ceasefire remains shaky.

Still, an even bigger tragedy eventually unfolded in Syria.

That same spring in 2011, opposition protesters to the Alawite dictatorship of Bashar Al-Assad took to the streets of Syria’s cities. At no point did President Obama urge Syrians to overthrow Assad or promise American intervention to topple Assad or even halt the growing humanitarian crisis. Nevertheless, Syrian opposition forces believed the Libya precedent made international military assistance to their cause inevitable. As one Syrian National Council spokesperson put it, “We expect the international community to act in Syria as it did in Libya.” SNC President Burhan Ghalioun similarly declared, “If the regime continues killing people, the international community will have to intervene, as it did in Libya.” In 2012, the founder of the Free Syrian Army, Colonel Riad al‑Asaad, was counting on help from the United States and the West when he proclaimed, “We want a safe zone and a no‑fly zone like Libya. The world will not leave us alone.”

But the world did leave the Syrian people alone in their fight against Assad. And this came after the statements from President Obama and Secretary of State Hillary Clinton in the summer of 2011 that “the time has come for President Assad to step aside” and had “lost legitimacy.” But even after the exhaustive debates in 2012 and 2013 about arming the Syrian rebels and Obama’s recklessly casual remark that the regime’s use of chemical weapons would constitute a “red line” triggering American intervention, the U.S. and its NATO allies largely stood on the sidelines.

Russia and Hezbollah, Assad’s Iranian-backed Shiite allies in Lebanon, did not. The result was the rapid rollback of opposition gains and a bloody civil war that only ended with Assad’s collapse last year. And over the ensuing 14 years, some 500,000 Syrians were killed in the cataclysm, with an estimated 13 million more—half of the pre-war population—either internally displaced or forced to leave Syria as refugees.

The lessons for the United States and the American people are clear. Even with the best of intentions, post-intervention reality on the ground following regime change may be more violent, more unstable and more dangerous for the region than anyone understood or predicted. And as the suffering of the Iraqi people in the 1990’s and the Syrians in over the past 15 years has revealed, American failure to live up to its promises of help—real or perceived—can lead to catastrophe.

Nevertheless, President Trump has continued his bellicose talk regarding Iran even as the United States military is repositioning forces in the region who could be vulnerable to counter-strikes from Tehran. But even if direct military intervention is not forthcoming from the United States, covert action and cyber operations could still produce blowback in Iran that no one anticipated. After all, in 1953 the U.S. and the U.K. carried out a clandestine operation to overthrow the constitutionally elected Prime Minister Mohammed Mossadegh of Iran, all in order to curb Russian influence and reverse Tehran’s nationalization of the country’s oil industry. And we all know how that worked out.