President Donald Trump made the right decision in responding militarily to Syrian dictator Bashar Assad’s latest chemical-weaponsattack, which killed dozens of civilians. Assad’s henchmen unquestionably violated decades-old prohibitions against the use of such weapons as well as an internationally-brokered agreement Assad signed promising to surrender his WMD arsenal. That fact serves as a reminder that neither the attack nor the U.S. response occurred in a vacuum. Rather, both are part of long chain of actions and inaction.

The agreement Assad made to give up his chemical weapons—conceived with the blessing of Vladimir Putin’s Foreign Ministry in September 2013, after the gassing of Ghouta—was hailed by President Barack Obama as “an important concrete step toward the goal of moving Syria’s chemical weapons under international control so that they may ultimately be destroyed.” He warned that “if diplomacy fails, the United States remains prepared to act.”

Some of us had serious doubtsabout the deal, which was implemented by the Organization for the Prohibition of Chemical Weapons (OPCW). The intervening years have confirmed those doubts. Even before the April attack, Assad had violated the agreement throughout the second half of the Obama administration.

Less than two years after OPCW began its work, proof of the deal’s utter failure was everywhere. The Washington Post, June 20, 2015: “Barbarism with chlorine gas goes unchecked in Syria.” Voice of America, June 17, 2015: “Syrian doctors present evidence of new chlorine gas attacks to U.S. Congress.” The Economist, May 13, 2015: “The gassing continues.” Reuters, May 8, 2015: “Weapons inspectors find undeclared sarin and VX traces in Syria.” The New York Times, May 6, 2015: “Two years after President Bashar al-Assad agreed to dismantle Syria’s chemical weapons stockpile, there is mounting evidence that his government is flouting international law to drop jerry-built chlorine bombs.”

But Obama, tragically, did nothing in the years after Ghouta to punish Assad or call Putin to task.

It’s tragic not only because of the death and destruction, but also because Obama had warned Assad that using chemical weapons would be a “red line” for the United States. Thus, after the Ghouta attack (which killed 1,400 people), Obama explained that Assad’s use of chemical weapons posed “a serious national security threat to the United States,” that “a failure to stand against the use of chemical weapons would weaken prohibitions against other weapons of mass destruction,” and that “it is in the national security interests of the United States to respond to the Assad regime’s use of chemical weapons through a targeted military strike.” Such a strike, the president explained, would “send a clear message not only to the Assad regime, but also to other countries that may be interested in testing some of these international norms.”

Obama, it seemed, recognized the importance of reinforcing the taboo against the use of chemical weapons—and the confluence of U.S. interests and ideals in Syria.

But then he engaged in a prime-time debate with himself and punted the problem to Congress. Make no mistake, seeking congressional support for military action—something the much-maligned Bush administration did before Afghanistan and Iraq—is the preferable way to go to war. However, other precedents—Reagan in Grenada, the elder Bush in Panama, Clinton in Kosovo, Obama himself in Libya and Iraq—underscore that congressional authorization was not essential after Ghouta.

Obama sought a way out of this conundrum of his own making by accepting Putin’s promise to cajole Assad into handing over his WMDs. But entrusting an untrustworthy regime to vouch for the disarmament of another untrustworthy regime was something like asking a serial killer to hand over his bullets, letting him keep the gun, allowing him to avoid prosecution and prison, and trusting one of his accomplicesto keep track of the ammo.

Fast-forward to today. Even though Citizen Trump urged Obama after Assad’s 2013 use of chemical weapons, “Do not attack Syria…there is no upside and tremendous downside,” President Trump ordered a punitive military strike against the Syrian regime because he recognized, in a striking echo of his predecessor’s assessment of the situation, that “it is in the vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.” But the “America First” president also conceded that he acted to defend ideals and values: “Babies were cruelly murdered in this very barbaric attack. No child of God should ever suffer such horror.”

For all his flaws, Trump seems to understand that actions are the only thing that matter when dealing with the likes of Assad. As then-Secretary of State John Kerry said after Ghouta, “It matters if nothing is done.”

Regrettably, because Obama did nothing after the gassing of Ghouta, many options that existed in 2013—striking command-and-control facilities, grounding or erasing the Syrian air force, targeting key nodes of regime power in Damascus—are off the table today because Russian personnel and assets are spread across Syria, most co-located with Assad’s military. Thus, the U.S. military had to pre-informits Russian counterparts of the impending missile strike. Doubtless, Russian commanders shared the news with their Syrian friends, sparing the guilty parties and preserving their instruments of murder. Indeed, Assad has dispersed his air force since the punitive U.S. missile strike.

It’s also important to note that Putin didn’t intervene in Syria until 2015. Obama’s erased “red line” surely played a role in that decision. Whether the U.S. should have avenged Ghouta or protected Aleppo or toppled Assad is open to debate, but the importance of U.S. credibility is not. Obama failed to grasp this; Putin acted accordingly.

If you subscribe to the notion that U.S. foreign policy should be based solely on interests, it’s easy to avert your gaze from Syria’s hellscape. But as the new president has learned, it’s much harder justifying a Pilate-like approach for those who wrestle with the headlines and believe the civilized world is called to defend more than narrow interests.

A version of this essay appeared in Providence.