The challenge for the people of Syria — besides staying alive, of course, in a civil war that has killed 130,000 of them and displaced millions — is to get the rest of the world to pay attention. Month after month, the killing grinds on and those outside Syria look the other way, either distracted or paralysed by the sense that there is nothing that can be done.

It takes something very grave and very shocking to break through that torpor. Last August, it was the apparent chemical attack on the Damascus suburbs of Ghouta, killing an estimated 1,400 people— including more than 400 children. Now comes the report of three former war crimes prosecutors, saying they have seen compelling evidence of the systematic murder of 11,000 detainees through starvation, beatings and torture, including the gouging out of eyes and electrocution — and all that in just one part of Syria, with international aid agencies telling the Guardian they fear this is merely the tip of a large and gruesome iceberg.

The source of the evidence is hard to fault: He is a former photographer for the Syrian regime who has defected. The report’s authors, who interviewed the source for three days, have no obvious axe to grind and are eminently credible — they served as prosecutors at the criminal tribunals on former Yugoslavia and Sierra Leone. Those facts will surely offset any misgivings over the report’s origins: It was commissioned and funded by the government of Qatar, a player in the Syrian conflict on the anti-government side. The evidence is too overwhelming and the reputations of those who have assessed it too strong, for this report to be dismissed as Qatari propaganda (though some will try). Above all, it is the nature of this evidence that will have the greatest impact. One of the report’s authors, Desmond de Silva QC, told Radio 4’s Today programme that the photographs were “reminiscent” of the first images of the Nazi concentration camps liberated in 1945. The pictures of emaciated corpses reinforce his point. Similarly, it was the notion of children being gassed to death, which struck such an emotive chord when the Ghouta massacre was revealed last year. It seems we have an unspoken measure when judging atrocity. Anything which evokes memories of the Holocaust enters a specially dark category. Which is why this, like Ghouta, may break through the lethargy and inertia that has blanketed so much discussion of Syria. Ghouta prompted US President Barack Obama to say, in effect, a “red line” had been crossed and to threaten military action — which at one point seemed imminent. What will be the consequence now?

There is still little appetite for armed intervention. David Cameron ruled it out after that post-Ghouta Commons defeat. In an interview in the current edition of the New Yorker, Obama said of the prospect of action then: “It is very difficult to imagine a scenario in which our involvement in Syria would have led to a better outcome, short of us being willing to undertake an effort in size and scope similar to what we did in Iraq.” There is no reason to expect him to have changed that view now.

Instead, the best hope is for a diplomatic breakthrough. The Geneva II talks, which opened yesterday — and which doubtless explain the timing of the torture photos’ release — could hardly enjoy lower expectations, especially as the warm-up act has been a disinvitation to the Iranians. Nevertheless, the eventual outcome of the post-Ghouta flurry of activity could be an encouraging precedent. The threat of American military action led last September to a joint US-Russia initiative to disarm the Bashar Al Assad regime of chemical weapons, one that defied the predictions of immediate failure.

There is no reason why similar international determination could not produce similarly substantial progress.

The key now, as then, is Russia. If Vladimir Putin decides that his interests are no longer served by unqualified indulgence of Al Assad, and he orders him to stop this kind of slaughter, then it will stop. It happened before, when Putin demanded the handover of chemical weapons, and it can happen again. But first Russia needs to feel the heat of global outrage. These photographs and the horrific story they tell may just generate it.

Guardian.