Watching cable coverage of the possible military strike on Syria, my wife noticed a repeated verbal slip: People kept saying “Saddam” when they meant “Assad.”

As Secretary of State John Kerry pointedly acknowledged in his speech Friday, the debate is taking place in the shadow of the Iraq War that started 10 years ago. If we hadn’t invaded Iraq, chances are that we would be in Syria. Now, though, opponents of U.S. military action are warning that it could turn out to be the needless disaster that most people take the Iraq War to have been. That’s unfair. Kerry’s lengthy defense notwithstanding, a military campaign in Syria has a lot less going for it than the invasion of Iraq did.

I count at least six important differences between the two situations.

First, there’s no clear objective. At least in Iraq, we knew what our initial goal was: overthrowing Saddam Hussein’s regime. This time, our government is disavowing any such concrete purpose. We’re instead going to be “punishing” Bashar Assad’s regime or “sending a message” to it. It’s the armed forces as Western Union. How we will know when the regime has been punished enough, or the message made unmistakable, is anyone’s guess.

Second, the national-security rationale for intervention is weaker in Syria. In Iraq, of course, the national-security claims turned out to be vastly overstated; the regime didn’t have the nuclear capacities that Western intelligence agencies suggested. This time, though, not much of a national-security argument is even being made. It has been pointed out that the Syrian regime is an ally of Iran, but that’s hardly a reason for an intervention that is not designed to replace the regime with one friendlier to us. President Barack Obama has tried claiming that Syria’s chemical weapons could be turned against us, but it’s not clear he has even persuaded himself to worry about that.

Third, we had more international support for the Iraq War than we would now have in Syria. The U.S. Republican-British Labour alliance of a decade ago is not being succeeded by a U.S. Democratic-British Tory alliance.

Fourth, the Iraq invasion had public support. Just a few weeks beforehand, an ABC-Washington Post poll found that 59 percent of the public thought we should “move soon to disarm Iraq and remove Saddam Hussein from power, by war if necessary, working with countries that are willing to assist, even without the support of the United Nations.” Other polls told a similar story, although some of them found a stronger desire to wait for U.N. approval.

By contrast, Reuters-Ipsos polls have consistently found that a plurality of Americans oppose intervention in Syria even when the regime’s use of chemical weapons is mentioned. Don’t mention it, and support drops even lower. The NBC-Wall Street Journal poll, which also found majority support for action against Iraq in 2003, shows majority opposition to action in Syria now.

Fifth, a prolonged public debate preceded the Iraq invasion. President George W. Bush and his top officials made their case for the war repeatedly, and anti-war protesters made the case against. It was the main subject of debate during the 2002 congressional election campaign. Many people, especially in retrospect, think that advocates of the Iraq War manipulated the conversation, but at least it took place. President Obama, in contrast, has barely discussed the Syrian crisis with the public. If we take action in Syria, it will be the first time many Americans learn that it’s even under consideration.

Sixth, Congress authorized the Iraq War in a bipartisan vote: Two-fifths of House Democrats and a majority of Senate Democrats voted for the resolution, along with almost every Republican. President Obama, according to his spokesman Jay Carney, doesn’t think he needs congressional approval: Consultation is enough. It seems highly likely that if Congress did vote on Syria, a majority wouldn’t back U.S. military action.

There are some contrasts with the Iraq War, I admit, that make an attack on Syria look better. Because we wouldn’t be mobilizing to end the regime, our military commitment would be smaller and probably our losses as well. It’s also worth noting that some people are calling for a more robust military engagement to bring about an eventual change of regime. Some of the arguments that apply against a limited strike wouldn’t apply to that course of action.

But bigger intervention would raise objections of its own, including one learned in Iraq: the danger of state disintegration. (I’m indebted for this point to David Frum, who made it on Twitter.) Supporters of the Iraq War thought we would just hand over the country’s government to new leaders. What actually happened — the state collapsed, and the U.S. had to pick up the pieces — didn’t figure in the debate at all.

This time, we ought to know that if military action leads to the end of Assad’s regime, our limited engagement could quickly expand.

Ramesh Ponnuru is a Bloomberg View columnist and a senior editor at National Review.