It seems an age since there was any positive news about Syria, but the unveiling yesterday morning in London of a transition plan for rebuilding the country from the Syrian opposition High Negotiation Committee (HNC) provided a glimmer of light in the darkness. It is a really robust plan, which learns from past mistakes of reconstruction efforts in the region, and aims at a genuinely inclusive transitional government and elections after 18 months. I’m glad the UK seem to be backing the plan, and hope it can provide some focus to the ongoing ceasefire talks.

But still, for the most part, to talk about Syria today is to wade into a situation so horrendous and so complicated that it almost defies analysis. Our emotional responses to images of human suffering clash with the rational need to make sense of what is happening and who is responsible. Another desperate picture from Aleppo captured the front pages over the summer, causing a human response that rippled around the world, uniting us is grief, despair and outrage. These emotions, this heart-wrenching sorrow and anger, must be central to our response to Syria, but when they are misdirected or badly informed they can hold us back.

One of the more common response to the recent situation in Aleppo has been condemnation of Labour MPs who voted for airstrikes against Daesh in Syria earlier this year. People who supported this action against these theological fascists in northern Syria are being told they are somehow responsible for President Assad’s brutal killings of civilians in Aleppo. Britain, it is claimed, is ‘bombing Syria’ and therefore we are responsible for any civilian casualties in that country.

But this claim is utterly untrue. British airstrikes have resulted in no civilian casualties, they are hundreds of miles from Aleppo where the worst suffering is occurring. The vast majority of civilian casualties, including those in the worst images, are victims of Assad’s aggression against his own people, sparked by the democratic uprising of the Arab spring. Surely even those whose political activism is mainly Facebook and Twitter commenting can recall that, in 2013, the House of Commons had a full debate on British involvement in possible action against Assad. Labour did not support David Cameron, and our country has taken no overt military steps to respond to Assad’s brutality.

In fact, like many in our country, I wrestle not with what less, but with what more we could have done to stop Assad. The latest stories of life and death in Aleppo drive me mad with worry. If I am asked (as I am sure all MPs are, now that Twitter dominates debate), ‘how do you sleep?’, the honest answer is: not well. Not well at all.

Because, there is no clearer picture of the political horror that is Syria — always for me an ever-present worry — than the muted reaction to the latest wave of chemical attacks on civilians. Have we become unshockable, numb to atrocities, unmoved by the war crimes that have become routine in that country?

The world shrugged a few weeks ago when a report from Human Rights Watch revealed that incendiary weapons similar to napalm are being dropped on civilians in the opposition-held areas of Aleppo and Idlib. Napalm. It sounds like a weapon from another age, but this is the Middle East in the twenty first century and it is on fire.

It isn’t just napalm either. August saw the re-emergence of chlorine gas as a weapon with barrels of the lethal toxin dropped on densely populated civilian areas. The gas disperses quickly and fills the lungs of people who inhale it with fluid until they choke. Its availability makes it easy to mass produce and almost impossible to trace. As a result, chemical weapons experts are warning of the risk of ‘normalising’ chemical weapons after a sustained international effort to keep them beyond the pale. Meanwhile Syrians on the ground talk of hearing the sound of helicopters and praying they are just carrying explosives and nothing worse.

It is important to be clear not just about what is happening in Syria, but also who is doing it and where our anger and our action should be directed.

What we are witnessing is Assad’s regime, supported by his allies, ruthlessly slaughtering thousands of its own people with illegal chemical weapons. No other force in Syria uses the helicopters that are being used to perpetrate these crimes and it is almost exclusively opposition areas that are being targeted.

Clarity is necessary because confusion results in equivocation, indecision, and inaction. When the Serbs were slaughtering thousands in Bosnia, international action was delayed by false claims that Bosnian government forces were staging attacks against civilians to try to provoke an international response against Karadzic. The result was the Major government, to its lasting shame, opposing arms sales to the Bosnians, resisting a no-fly zone and drawing moral equivalence between the victims of genocide and the perpetrators.

That is why the recent publication of the Joint Investigative Mechanism (JIM) report into chemical weapons in Syria is so important. This UN report definitively names the Assad regime as the perpetrator of these atrocities. This is a moment demanding a meaningful response from the international community, despite the inevitable Russia opposition. Responding to barrel bombs with press releases is not good enough. There has to be a red line, and a recognition that crimes on this scale demand accountability.

This will be one of the first big foreign policy tests for Theresa May and the new government. The UK debate about Syria has mainly focused on the fight against Daesh, and the plight of the refugees fleeing the ruin of their country, almost completely ignoring the regime and its atrocities. New foreign secretary Boris Johnson has condemned the attacks as “utterly abhorrent” and said Britain “will work with the UN and other partners to establish the facts and hold those responsible to account”, but what does this mean? How will Assad be held to account? Despite the shameful Russian blocking in the UN Security Council, the eyes of the world will be on the international community to see whether there really are sanctions for chemical weapons use or whether the next murderous dictator feels emboldened to emulate Assad’s brutality.

Protection of civilians from aerial bombardment, along with the destruction of chemical weapons stockpiles, must be the aim. There is a legal precedent in Kosovo for the establishment of a no-fly zone without UNSC backing and this option should not be off the table if it can be shown to be the most effective way of protecting civilians. But even failing this there are things we can do. We can push for bigger windows to get humanitarian aid into the worst hit areas. We can get support to the heroic white helmets, the Syrian volunteers who risk their lives to save as many people as they can from the death raining down on them. We can offer clear support to the credible, inclusive plans the Syrian opposition are putting forward.

As an absolute minimum, we simply cannot fail to meet the Government’s 20,000 by 2020 agreement on resettlement for Syrian refugees. The slow pace with which our responsibilities are being met is not good enough. And Theresa May’s first act of sacking the minister for Syrian refugees and not replacing him does not show good intent.

Nor does the almost total silence of the new International Development Secretary on this subject. What does she have to say about the 2.5 million Syrian refugee children who have been displaced since the start of the conflict, most of whom have neither sanctuary here nor basic facilities where they are? We could be doing more, much more quickly.

On London’s south bank there is a memorial dedicated to the International Brigades: those who fought for democracy in the Spanish Civil War. On one side of the sculpture there is an inscription that reads: ‘They went because their open eyes could see no other way’.

With the advent of social media images of horror can be passed amongst millions in minutes. Like many who have campaigned on internationalist issues, I had hoped that the world’s eyes would be opened wider to today’s atrocities and injustices than they have been in the past.

Whether or not this is true, it now seems that it is not open eyes, but the desire for action that is lacking. We be clear about who is to blame and what can be done and must not waste a moment in arguing for it.