Whatever his faults, no one can charge Syrian President Bashar Assad with inconsistency.Six years ago, early in the war Assad initiated against his own citizens, his forces would open fire on protesters who gathered on the streets of Damascus and other cities after Friday prayers.Then on Saturday, they would shoot and kill demonstrators accompanying the funeral processions for those murdered the day before.The chemical-weapons attacks in Idlib last week fit that gruesome pattern. First, an attack on a neighborhood left dozens dead or severely wounded, including many children.Then came a bombing, with a chemical substance, of the clinic where the suffering victims of the first attack had been transferred for urgent care. Main hospitals in Idlib already had been severely damaged in previous assaults.Following the regime’s violent capture of Aleppo in December with the help of Iranian and Russian forces – which added more than 30,000 refugees to the six million already internally displaced, not to mention the five million who have left the country – Stefan de Mistura, the UN envoy to Syria, noted that Idlib “could in theory be the next Aleppo.” He was right.Assad has consistently used every weapon available to him to pursue his costly retribution against the Syrian people. Despite the naïve beliefs by some in the international community, he never fully complied with the international demand to hand over Syria’s large chemical weapons stockpile to the US and Russia for destruction, and his regime used chlorine gas in a number of attacks. Now, it has used sarin in Idlib, causing casualties similar to those inflicted on a Damascus suburb in August 2013. “More than 14,000 people have been subjected to chemical weapons attacks, and more than 1,500 have died” since the war began, Ahmad Tarakji, president of the Syrian American Medical Society, wrote in a New York Times op-ed after the Idlib atrocity.Idlib also revealed again the inconsistencies in US policy toward Syria and the sharply divided international response to the war, both of which have played into Assad’s hands. The Obama administration shifted from adamantly demanding Assad’s resignation to quietly accepting the status quo. President Trump’s Syria policy is evolving, from initially not challenging Assad’s legitimacy to the dramatic decision last Thursday to attack a Syrian airbase with 59 missiles.“There can be no dispute that Syria used banned chemical weapons, violated its obligations under the chemical weapons convention and ignored the urging of the UN Security Council,” said Trump, visibly angry and shaken by the slaughter of children.Trump correctly said that “years of previous attempts at changing Assad’s behavior have all failed,” but it is still very unclear whether this US military action will begin to genuinely alter the situation on the ground, and what additional steps are planned to influence Assad and his principal allies.Iran and Russia, co-authors with Assad of the Syrian carnage, and joined by the terrorist proxy Hezbollah, are far more interested in exploiting the conflict to advance their respective national interests than in assuring the welfare and security of the Syrian people.Recent diplomatic clashes in the UN Security Council chamber, in the safety of New York City, show why the Syrian conflict is so hard to resolve. US Ambassador Nikki Haley, like her predecessor ambassador Samantha Power, is dealing with a Russia so steadfastly supportive of Assad that it regularly vetoes resolutions and propagates alternative narratives about the Syrian reality.“How many more children have to die before Russia cares?” Haley told the council on April 5, in her latest condemnation of Russia’s support for Assad. “If Russia has the influence in Syria that it claims to have, we need to see them use it. We need to see them put an end to these horrific acts.”While France, the United Kingdom and other Western powers have joined the US in expressing horror over the Idlib attacks, Russia dismissed the allegations against Assad, arguing that the deadly chemicals were released when a Syrian air-strike struck a bomb-making “terrorist warehouse” that housed toxic substances. As such incredible statements are issued from Damascus and Moscow, innocent Syrians continue to die. To date, the lack of a united response has not only dangerously emboldened Assad, but it has also likely encouraged the leaders of other countries, such as North Korea, that can deploy weapons of mass destruction, to advance their own perceived national interests with little fear that the international community will stop them.What happens in Syria does not stay in Syria. That’s why the US must continue to speak out, make every effort to convince world leaders to join in ending the nightmare, and to show unambiguous leadership and resolve.The writer is the American Jewish Committee’s director of media relations.