In Syria, elite army units are bloodily assaulting a now-armed resistance. Supporters of dictator Bashar al-Assad are being picked off in targeted assassinations while opposition activists are tortured to death. Western countries stand fecklessly by as Russia and China veto action by the U.N. Security Council. At least 2,900 dead have been counted — and the carnage may be just getting started.

I could write a column about all of this. But I’d like to propose, instead, that we think again about the war in Iraq.

With U.S. troops less than three months away from withdrawal, that mission is now generally regarded in Washington as, at best, a waste of American lives and resources, and at worst a monumental folly — and that’s among the Republican presidential candidates. But the misnamed Arab Spring, which has turned from a euphoric winter in Tunisia and Egypt to a savage summer in Libya, Yemen and Syria, casts Iraq in a different light.

It turns out that the end of autocracy in the Arab Middle East, unlike in Central Europe or Asia, will not happen peacefully. People power isn’t working. Dictators such as Assad, Moammar Gaddafi and Yemen’s Ali Abdullah Saleh, backed by mountains of weapons and armies bound to them by tribe or sect, prefer to fight to the death rather than quietly yield. Despite seeing Hosni Mubarak in his courtroom cage — or maybe because of it — they don’t shrink from crimes against humanity.

The carnage might be seen as regrettable but acceptable if the bad guys were losing. But with the notable exception of Gaddafi, they are not. Assad has been written off by most of the West’s intelligence services, but his tanks and artillery are proving more than a match for the ragtag groups of army defectors in towns such as Homs and Rastan. Saleh was nearly killed by a bomb, but on his return after three months in a Saudi hospital, forces commanded by his son still held the presidential palace in Sanaa.

Gaddafi, of course, is losing, though still at large — thanks to the military intervention by NATO. When the air campaign began last spring, he was on the verge of massacring the opposition in the rebel stronghold of Benghazi. Western planes and drones proved just enough to tip the balance against him. But Libya was the limit for the Obama administration, Britain and France: There will be no such operation in Syria or Yemen, goes the constant refrain.

This means that the bloodshed in those countries could drag on indefinitely, and grow steadily worse. Tribal war, and the anarchy of nearby Somalia, beckons for Yemen. In Syria we could see, at worst, a repeat of the history of Lebanon: sectarian war, interspersed with interventions by neighbors and transnational operations by terrorists.

This brings us back to Iraq. As former Bush administration strategist Meghan O’Sullivan recently wrote in The Post, Iraq has fallen well short of both American and Iraqi expectations. The pain and cost of that war are some of the reasons the United States and its allies have sworn off intervention in Syria and why the Obama administration made a half-hearted effort in Libya.

Iraq, however, looks a lot like what Syria, and much of the rest of the Arab Middle East, might hope to be. Its vicious dictator and his family are gone, as is the rule by a sectarian minority that required perpetual repression. The quasi-civil war that raged five years ago is dormant, and Iraq’s multiple sects manage their differences through democratic votes and sometimes excruciating but workable negotiations. Though spectacular attacks still win headlines, fewer people have died violently this year in Iraq than in Mexico — or Syria.

Just as significantly, Iraq remains an ally of the United States, an enemy of al-Qaeda and a force for relative good in the Middle East. It is buying $12 billion in U.S. weapons and has requested that an American training force remain in the country next year. It recently helped get two U.S. citizens out of prison in Iran.

All of this happened because the United States invaded the country. Saddam Hussein demonstrated how he could handle a homegrown, Arab Spring-style rebellion when he used helicopter gunships to slaughter masses of Shiites in 1991. Even had his regime somehow crumbled, without the presence of U.S. troops nothing would have stopped Iraq from spiralling into the bottomless sectarian conflict that now threatens Syria.

The Arab Spring, in short, is making the invasion of Iraq look more worthy — and necessary — than it did a year ago. Before another year has passed, Syrians may well find themselves wishing that it had happened to them.