ON TUESDAY, the world awoke - once again - to graphic images of dead and dying Syrian children, their pale, listless bodies bearing no marks of traumatic injury.

These were the innocent victims of a chemical weapons (CW) attack on the town of Khan Sheikhoun in Syria's Idlib Province - which, according to recent estimates, left at least 70 people dead, and constituted the worst attack since that in the Damascus suburb of East Ghouta in August 2013, which claimed more than 1,200 lives.

This horrific attack is only the latest in scores of chemical munitions attacks either alleged or verified to have been conducted by the Syrian regime since 2014.

Last year, the Organization for the Prohibition of Chemical Weapons (OPCW) and the U.N. Joint Investigative Mechanism (JIM) officially concluded that the Syrian Arab Armed Forces were responsible for three chemical weapons attacks in 2014 and 2015, in part because these attacks involved the use of helicopters (which only the Syrian government possesses) to deliver chlorine-laden munitions.

Human Rights Watch documented at least eight other chemical attacks between November and December 2016 associated with the Syrian government's assault on Aleppo.

Since January 2017, the OPCW Fact-Finding Mission (FFM) in Syria has also recorded eight alleged uses of chemical weapons.

Even so, on February 28, Russia and China vetoed a United Nations Security Council Resolution designed to sanction parties verifiably assessed by the OPCW-U.N. joint investigative mission to have carried out chemical attacks.

So is it any surprise that the Assad regime felt emboldened to continue using chemical weapons? Or that it has perhaps escalated to the use of even more toxic substances than chlorine, which has been its "go-to" chemical since the international community removed and destroyed its traditional military chemical arsenal in 2014?

This escalation in CW use fits a pattern observed on multiple occasions over the last several years. When the international community, particularly the United States, seems distracted, the Syrian regime feels emboldened to seek battlefield gains through chemical attacks, particularly in areas where the regime's military progress through more conventional means has stalled.

Why does the Assad regime do this? Because it works.

It is insufficient to frame the casualties in these attacks solely in terms of those affected by chemical agents. First, the psychological effects of these chemical attacks, and the added risks they pose to children and the elderly, are devastating.

Second, like many previous episodes, this one reportedly involves conventional targeting after the chemical attacks, which flushes civilians out of sheltered areas and makes them vulnerable to conventional bombing. To then target hospitals receiving the injured compounds the psychological effects.

This two-pronged tactic ensures that besieged civilians feel they have no place to hide and nowhere to protect their children.

Much has been made of the symptomology and increased lethality of the Khan Sheikhoun attack, raising questions about a possible secret production capability or stockpile of undeclared chemical weapons - notably sarin.

We should not engage in armchair diagnoses from YouTube videos. On-the-ground investigators can return a definitive assessment, and they need to be empowered to do their jobs.

The use of sarin or other traditional warfare agents would clearly signal that Assad believes he can operate with impunity. Chlorine - or any weaponized chemical used in this way - is just as heinous and legally prohibited. But nerve agents are more deadly and, unlike chlorine, require precursors that were supposed to be removed and destroyed in 2014.

That process eliminated the majority of Syria's military-scale chemical weapons program, but we can never know if everything was removed - as Syria, with Russian cover, continues to stall, obfuscate, mislead, and otherwise violate international obligations.

Moreover, the Syrians, with extensive military and scientific expertise in chemical weapons, are perfectly capable of developing improvised munitions and agents if they believe chlorine isn't getting the job done.

If it turns out that traditional military or improvised agents were used in these attacks, the implications are broader, and the audacity of the Syrian regime even more flagrant, but the crime is no more egregious.

We can debate what should have been done in the past, but it's far more important to act now.

We should expect such attacks to continue, and possibly increase, until international resistance builds and cleavages surface with the regime's patron, Russia. Then, perhaps such chemical use will again temporarily recede.

The international community must increase and sustain the pressure so that he is unwilling or unable to resume the attacks.

The United States must push for action in the Security Council and hold Russia to account for shielding Assad's atrocities. The Trump administration should insist on the immediate insertion of investigators on the ground to gather critical physical evidence, interview witnesses and victims, and ensure that the full record of these crimes is not lost.

The Russian theory that the massacre resulted from the bombing of a rebel-held chemical weapons storage facility seems highly implausible, but could be verified or refuted easily with a swift investigation.

In addition, the international community should demand the grounding of Syrian aircraft, particularly helicopters, which have served as the principle delivery vehicle for chemical munitions.

Sanctions should target the Syrian government, and individuals and entities with links to these atrocities, at the organizational and individual level.

The United States took an important step along these lines in January when it sanctioned 18 senior Syrian officials and five military branches associated with the Syrian regime's use of chemical weapons. We should do more and encourage other nations to do likewise.

Finally, the international community must support and develop a robust evidence repository and victim registration to ensure that these crimes are fully documented and evidence preserved in hopes that the arms of justice can reach these war criminals in the months and years to come.

Presidents inherit problems and unfinished business. President Barack Obama inherited two Middle East wars and an economic crisis of proportions not seen in decades.

President Donald Trump has inherited a North Korean regime undaunted by international pressure and hell-bent on acquiring missile and nuclear capabilities to threaten the United States. He has also inherited a catastrophic war in Syria in which atrocity and criminality seemingly have no limits.

Casting blame and pointing fingers will not save a single child's life, bring justice to a single grieving mother, or return a single refugee to his home. Nor will it convince adversaries that the price to be paid for resorting to chemical weapons, or biological or nuclear weapons, will exceed any benefits from their use.

Deterring future chemical weapons use requires hard work, tenacity, and, most importantly, leadership - not recrimination or revisionism.

This is too important.