There’s no way the United States can avoid it anymore. Acting on Syria is essential.

The horrific cell phone videos and still photographs of Syrian men, women and children writhing in agony and presenting the classic symptoms associated with poison gas said it all.

Secretary of State John Kerry said Monday that there was “clear evidence” that the regime of Syrian President Bashar Assad had indeed used chemical weapons to attack his own citizens in the suburbs of Damascus, a “moral obscenity” that has shocked the world’s conscience.

Casting aside diplomatic niceties, Kerry accused the Syrian regime of the “indiscriminate slaughter of civilians,” and of cynical efforts to cover up what he called a “cowardly crime,” as reported in Tuesday’s New York Times.

President Barack Obama indicated a year ago that if Syria indeed could be proved to have used chemical weapons against rebel forces in the two-year old civil war, that would “cross a red line,” and would be a “game-changer.” Back in April, a smaller scale attack was investigated by the United Nations and found to have been a chemical weapons attack, yet no U.S. or allied response was forthcoming other than a pledge to provide the rebels with small-scale “lethal weapons,” the delivery of which has not been confirmed.

In the most recent attack, Doctors Without Borders, a highly respected human rights and rescue group, could not yet confirm the exact chemical agents that were used by the regime, but said the symptoms reported by three medical facilities, which received 3,600 patients, were classic signs of chemical nerve gas poisoning. The patients had such symptoms as breathing difficulties, dilated pupils, convulsions, foaming at the mouth and blurred vision. Doctors Without Borders estimates that at least 300 and as many as 1,800 Syrians may have been killed in the apparent nerve gas attacks.

At this writing, it seems all but certain that a military response will be forthcoming, and this course of action has drawn support from U.S. allies, including Great Britain, France and Turkey. Key members of both Houses in Congress across the political spectrum have also voiced their insistence on a meaningful response.

Assad has warned that any U.S. or allied military intervention in Syria would result in the transformation of the Middle East into a “ball of fire,” and that the attack will be resisted and responded to with “all means necessary.” Russia, who has supplied arms to Assad, has cautioned the West over getting involved, but at this point, the potential for additional mass murders would appear to far outweigh concerns about Russia’s stance.

Daniel Balz, the senior correspondent at the Washington Post, expressed this view on “Meet the Press” Sunday, noting that the cost of not taking action has reached the point that it outweighs the risks of taking action. Richard Haas, head of the Council on Foreign Relations, usually extremely cautious about military intervention, said Monday on the “PBS NewsHour” that if the U.S. failed to act, its credibility would be damaged severely with both our allies and our adversaries.

It appears that several options are on the table. NATO is considered more likely to be the source of joint support than the United Nations, since any effort to get a Security Council resolution would almost surely face its usual veto by Russia and probably China. This is particularly unfortunate when one considers that U.N. Inspectors have not been provided safe passage to confirm the presence of chemical weapon residue.

There then remains the actual form of intervention. Military experts have stated that the use of offshore cruise missiles could be used to attack various sites in Syria, but that there would be no “boots on the ground.”  Some hawkish observers and commentators have called for a strong and sustained attack aimed at toppling Assad’s brutal regime. A more likely scenario is a measured but significant military response which would degrade Assad’s ability to stage similar attacks, and of sufficient strength to deter his regime from doing so.

Whatever form the action takes, there can be no serious doubt that action is absolutely essential. The United States and the civilized world cannot sit back and do nothing when innocent men, women and children are being murdered with chemical weapons in the most sustained and brutal manner since World War II.