President Trump once said the U.S. should stay out of Syria. Then he bombed airbases there. The case for strikes is better than the case for all out war.

On Thursday night the United States struck air bases in Syria with cruise missiles. This was done in retaliation for the use of chemical weapons against Syrian citizens.

Observers have noticed that President Donald Trump’s decision to attack Syria is at odds with his rhetoric over the last four years. Not only has he pushed a foreign policy that emphasizes American interests instead of humanitarian concerns, he’s specifically identified Syria as a place the United States should avoid invading. There are many examples of his arguments against action in Syria, but this tweet from June 2013 is representative:

We should stay the hell out of Syria, the “rebels” are just as bad as the current regime. WHAT WILL WE GET FOR OUR LIVES AND $ BILLIONS?ZERO — Donald J. Trump (@realDonaldTrump) June 16, 2013

Thursday also featured Secretary of State Rex Tillerson discussing “regime change” in Syria, and President Trump said the chemical attack in Syria on Tuesday “crossed a lot of lines for me.”

Interventionists such as Sen. John McCain, Sen. Lindsey Graham, and political commentator Bill Kristol were pleased with the strikes in Syria. For Trump supporters who had supported his rhetoric of restraint toward the region, it was a disappointment.

These people believed President Trump would steer a course different than the one adopted by the foreign policy establishment in both the Republican and Democratic parties.

However, there is a national interest case for striking Syria this week that is easier to make than the case for full-fledged war with Syria, which requires much more discussion and for which congressional approval should be sought. Some would argue that congressional approval should have been sought even for the limited strikes, and a representative case was made here in 2013 when the issue last flared.

That Syrian President Bashar al-Assad used sarin gas against civilians is significant in multiple ways. Yes, al-Assad has been brutally killing people for years, but the use of chemical weapons is a violation of a treaty Syria has signed, and a violation of a norm that Americans have an interest in upholding.

Assad’s government signed the global treaty that bans chemical weapons four years ago. He agreed to dispose of his chemical weapons, and the Obama administration claimed that Syria voluntarily did so completely just last year. President Barack Obama had talked about intervening in the Syrian civil war in 2013, but abandoned that plan after Syria signed the chemical weapons ban.

Assad’s use of sarin gas is a clear violation of that treaty, and the norm against chemical warfare is in the American interest to uphold. The best way to stop future use of chemical weapons and other weapons of mass destruction is to ensure that the American response is severe. The response should cause significantly more damage than any temporary advantage gained by their use. Americans live throughout the world and the country wants to make sure that no Americans or American interests are caught up in the use of weapons of mass destruction.

The case for larger intervention in Syria, however, is much more complicated and worthy of debate. As Sean Davis wrote in, “So You Want To Go To War In Syria To Depose Assad. Can You Answer These 14 Questions First?” Americans should have a clear understanding of goals and strategy before invading yet another country.

How is American interest served by deposing Assad? What will victory look like? How long will it take to achieve that victory? What military, diplomatic and financial resources will be required? Who else will join with America to depose Assad? Will war increase tensions with Russia or will the United States attempt to work with them on a shared goal in the region? What government will replace Assad and what role should the United States have in securing it? How will the United States ensure this invasion will work out differently than the failure to maintain victory in Iraq and Libya?

There is a national interest case to make for involvement in Syria, both to address the ISIS problem and the global refugee crisis, but the country must have a debate about whether it’s prepared to spend what it will take to accomplish those goals. Failure to have that conversation, much less have it honestly, is what has led Americans to get involved in too many regions without having the wherewithal to win those wars decisively.

Still, the use of limited strikes to retaliate for Assad’s use of chemical weapons in violation of a global treaty is not necessarily a major conflict with Trump’s previous foreign policy goals of restraint. The discussion of “regime change” and building of coalitions to depose Assad, however, is a major change.