Assad's crossing of the red line cannot go unpunished

For more than seven years, Bashar Al Assad has massacred the people of Syria with complete disregard. His reign of terror has decimated the country under a blanket of impunity supplied by Russia, which has repeatedly shot down diplomatic efforts to end the violence and bring its perpetrator to justice. What emboldened Damascus and Moscow, however, was the reluctance of the rest of the world to take punitive action. When evidence emerged in August 2013 that Mr Al Assad's forces had used sarin gas, then US president Barack Obama, who had perviously laid down a clear "red line" vowing to act if chemical weapons were deployed, failed to follow through on his promise. As his opponent John McCain said, it was "apparently written in disappearing ink". In Britain, Parliament voted against the government's proposal to intervene. This abdication of responsibility on humanitarian grounds gave the Syrian regime and Russia carte blanche to continue their slaughter unimpeded. The collective failure to act in 2013 has prompted the crisis we face now.

This is the context in which we must view the disturbing new images of Syrian children gasping for breath in yet another chemical attack. As Gavin Williamson, the British defence secretary, told The National this week in an exclusive interview, it is essential to recognise the "malign influence" in Syria of Russia and Iran. But even if Moscow and Tehran succeed in frustrating the UN's investigations, the clamour for a military intervention is growing louder by the minute. Yesterday Nikki Haley, the US ambassador to the UN, accused Russia of having the blood of Syrian children on its hands and pledged action against Mr Al Assad, regardless of the outcome of a UN Security Council resolution. Her statement was followed by US President Donald Trump saying he was considering "a lot of options militarily". In Britain, Prime Minister Theresa May condemned the chlorine gas attack as "barbaric"; across the channel, French President Emmanuel Macron looks poised to make good on his promise in February to retaliate militarily if proof of chemical weapons materialised.

A coalition of the willing against Mr Al Assad and his sponsors is rapidly coalescing. But it is important to recognise that today's Syria is a more complicated place than the one Mr Obama turned away from in 2013. The terrain is congested with the forces of multiple powers; it is a matter of pure luck that scrapes between Israel and Iran, the US and Russia and Turkey and US-backed Kurdish forces have not exploded into full-blown conflicts. A military intervention in such a place risks an escalation into outright warfare, which is why any action should be carefully considered and unity among the international community is essential. Yet if the proposed coalition of the willing does not intervene, there is a greater cost: the normalisation of chemical weapons. To let yet another red line be crossed without action could affect the course of history irrevocably.