Depending on your personal view, Aleppo has now fallen, or been retaken, or been liberated. But my interest is not with any political side. It’s with victims of state terror, and all the civilians whose lives have been shattered by a war that has been raging for more than five years. It is the most cynical conflict I have seen in 25 years of war reporting. Both the regime and opposition are guilty of war crimes, though one much more than the other.

What I’m considering now, from the comfort of my Paris home, is how a city falls. I am thinking of people cowering in basements and struggling with whether they flee from their city now, or wait. Who is coming to save them, or kill them? I know how that scenario goes. I lived through Sarajevo during the Bosnia war, and was in Grozny when it fell to (or was “liberated” by) Russian forces. I remember hiding in those basements waiting for the Russian tanks to come into the village, and wondering if I would be dead in a few hours.

I am thinking about the civilians – all of those people with whom I sat for hours while writing my book, or writing reports for the UN high commissioner for refugees – and what they are doing to survive.

My agonised frustration from watching the fall of Aleppo (or “retaking” it, in the words of the Syrian government) in real time was vented in a tweet I wrote: “Today I feel like a failure. Nearly 25 years reporting war crimes has added up to nothing. We said ‘never again’. What happened? #Aleppo”.

I use Twitter every day, but usually by re-posting articles of interest, and basically I only read tweets and articles on social media that are written about my region of speciality, the Middle East and north Africa. So when my tweet went viral I realised how many people misunderstood the Syrian conflict.

The response was a lesson in public awareness, and the failure of the international community – and our leaders – not only to do more to end the war, but to communicate this brutal crisis accurately. The war in Syria is not simply a war against terrorists – Isis and al-Nusra, the al-Qaida franchise in Syria – although this is the narrative the Russian Federation and its allies want us to believe. It started as a peaceful insurrection in 2011, an uprising in the long chain of the Arab spring, which turned to arms, and then turned into a civil war and a humanitarian catastrophe.

The US journalist Steven Sotloff in Bahrain. ‘I loathe Isis – they beheaded my friend Steve Sotloff, a journalist just doing his job.’ Photograph: Mazen Mahdi/EPA

While many wrote to me to express their horror at the plight of the thousands of civilians who are trapped in Aleppo and suffering untold horrors, many replied to say I was “terrorist scum”, a “terrorist lover” and that “Aleppo is now cleansed”.

One tweeter, called Partisan Girl, wrote: “You started supporting Al Qaeda and regime change wars. Abject failure.” So, she thought I supported al-Qaida? And she attributed this so-called support to the fact that I wrote about war crimes in Syria, from both sides? If my reading of her response is correct, then it has verified for me the twisted narrative that has been applied to the crisis.

Another tweeter wrote: “When I served in the US military, al Qaeda was the enemy, not the ally of our illegally baked regime change proxies.” Who, I want to ask, is backing al-Qaida? Not me, and not civilians who just want to get on with their lives and live in peace.

I want to write back to the trolls who are now calling me “terrorist scum” that I loathe Isis – they beheaded my friend Steve Sotloff, a journalist just doing his job, in 2014. I equally loathe al-Nusra. Both unleashed untold murderous brutality throughout Syria.

But terrorists are not civilians, as our leaders have led us to believe by failing to act because they thought it was too “complicated”. Syria has become a proxy war, but it could have been stopped long ago. Now, however, all the countries that have a stake in this war are more concerned with their vested interests than with the fate of people starving to death or being told: “Surrender or die.”

The international community has a lot to answer for. President Obama checked out, morally and otherwise, after the 2013 Ghouta chemical attacks on rebel-held areas of Damascus – which the UN confirmed was the worst chemical weapons attack in 25 years. He ruled out any kind of US-led ground invasion because: the war had become too messy; the rise of Isis; his own concerns over his domestic optics. He left a void that was filled, too quickly, by other world leaders, such as Vladimir Putin.

Except Obama missed the point. It wasn’t just another Middle Eastern war. The sorrow of Syria has now spread its web across the region, and into Europe. Aside from the millions of refugees, the thousands of homes destroyed, the millions of children who are uneducated, the millions whose lives were cut in half – and the roll call of the dead – you will now have the anger of Muslim people around the world who believe Aleppo was left to rot.

The difference with Sarajevo is that my journalist colleagues and I were able to make a difference, somehow, on policy (though our warnings about Srebrenica went unheeded until it was too late). Throughout this war my sense was that Barack Obama and David Cameron (and now Theresa May) were never listening.