President Trump did more than retaliate for Bashar al-Assad's illegal and inhumane use of nerve agents against civilians when he ordered the launch of 59 Tomahawk missiles to destroy al-Shayrat airbase in Syria. He also detonated a few shibboleths of his predecessor's foreign policy.

First is the idea that President Obama's 2013 deal to remove Assad's weapons of mass destruction was a success. Susan Rice and John Kerry have lauded the agreement with Russia to supervise the extraction and destruction of Assad's weapons stockpiles as recently as the last year. But Assad's brazen attack on civilians in Idlib Province exposed their celebrations as premature. Trump's swift, decisive, and limited response ended more than a half decade of vacillation toward's Assad's behavior. Obama diplomacy failed, but hard power may yet deter Assad from using weapons banned for almost a century.

The second casualty of the U.S. strike was the absurd Obama line that the only alternatives available to a president are inaction on one hand and a massive ground invasion and occupation on the other. Obama and the architects of his echo chamber would slam any advocate of military measures as a bloodthirsty warmonger ready to repeat the worst mistakes of the U.S. experience in Iraq and Afghanistan. But the reality has always been that there are a range of intermediary steps America can take to pursue her objectives and enforce the standards of Western civilization. The destruction of al-Shayrat is an example of coercive diplomacy similar to the airstrikes President Reagan deployed against Muammar Qaddafi and President Clinton deployed against Slobodan Milosevic. The immediate aim is punitive, to deter the further use of nerve gas against civilians. The longer-term goal is to remove Assad from power and reach a settlement that would in all likelihood partition Syria into sectarian zones of influence. Both objectives are impossible through diplomacy alone. Only through the introduction of force might we frighten the Syrians and their supporters into giving up Assad—if not the Alawite power structure—and winding down his war machine.

Which brings us to the final straw man Trump lit on fire. When President Obama punted on Syria in 2013, he claimed there was no international support for limited intervention. True, David Cameron lost a vote in Parliament on the matter. But the actual powers Obama didn't want to offend were Iran and Russia. He worried they would scuttle the Iran nuclear deal as payback. The loss of American credibility, the confidence of allies, and Syrian civilians were all factored into the cost of an Iranian promise not to test a bomb for 10 years.

Well, the rapprochement with Iran, if it ever existed, is over. In recent weeks President Trump has met with the leaders of our traditional Sunni allies: Saudi Arabia, Egypt, and Jordan. He has signed off on aid to Saudi in its war against Iranian proxies in Yemen. He has approved weapons to Bahrain, which is worried about Iranian influence over its Shiite population. America is heavily involved in Iraq and Syria. And now, by striking Assad, President Trump has targeted Iran's most prominent servant.

Where things go from here is anyone's guess. One of the reasons I urged Congress not to support Obama's airstrikes in 2013 was worry not only over the president's ambivalence but also possible escalation. Presidential ambivalence is gone, but my worry remains. I do think that this operation was about the best one could hope for: the message and objective was clear, the focus limited, the force overwhelming, support broad and deep. Assad may think twice before using these deadly agents again. Russia may be more inclined to replace him with one of his generals. But it is still worth thinking through possible responses if Assad crosses one of President Trump's many lines again. Whatever the future holds, we do know this: President Trump's foreign policy will look nothing like President Obama's.