Almost precisely one year ago, Assad unleashed chemical weapons against civilians in rural Idlib province, provoking international outrage and a symbolic, but still significant, missile strike ordered by Trump against the airbase from which the attacks were reportedly launched. Assad’s regime was responsible for the attacks and its Russian backers were fully in the know, later evidence suggested, but Damascus and Moscow lied wantonly in their hollow denials.

This weekend, it appears, Assad’s regime struck again. Fighters in Douma refused a one-sided ceasefire agreement, and haven’t buckled despite years of starvation siege warfare and indiscriminate bombing. In what has become a familiar chain of events, the regime groomed public opinion by airing accusations that the rebels might organize a false-flag chemical attack in order to attract international sympathy. An apparent chemical attack followed, killing at least 25 and wounding more than 500, according to unconfirmed reports from rescue workers and the Union of Medical Care and Relief Organizations. The Syrian government and the Russians have once again blamed the rebels, knowing that it will take months before solid evidence emerges, by which point most attention will have turned elsewhere. The pattern is by now predictable. In all likelihood, solid, independent evidence will soon emerge linking the attacks to the Syrian regime.

Assad already has unraveled the global taboo against chemical weapons, in the process exposing the incoherence of the international community. Syria has exposed the international liberal order as a convenient illusion. Western bromides of “never again” meant nothing when a determined dictator with hefty international backers committed crimes against humanity.

Why now? This latest attack in Ghouta, if it holds to the pattern, makes perfect sense in the calculus of Assad, Vladimir Putin, and Iran’s Supreme Leader Ayatollah Ali Khamenei. The successful trio wants first and foremost to subdue the remaining rebels in Syria, with an eye toward the several million people remaining in rebel-held Idlib province. A particularly heinous death for the holdouts in Ghouta, according to this military logic, might discourage the rebels in Idlib from fighting to the bitter end. Equally important, however, is the desire to corral Trump as Syria, Russia, and Iran did his predecessor, Barack Obama.

After the humiliating August 2013 “non-strike event,” when Obama changed his mind about his “red line” and decided not to react to Assad’s use of chemical weapons, the Syrians had America in a box. The White House signed up for a chemical disarmament plan that proved a farce. By the time the agreement had unraveled and Assad was back to using chemical weapons against Syrian citizens, the public no longer cared and Obama was busy discussing his foreign policy legacy.