We, like many people around the world, have been horrified by the tragedy of Ghouta unfolding before our eyes (Report, 1 March): children suffocating from chlorine gas, doctors collapsing in tears on the bloody floor of makeshift hospitals, and dazed civilians emerging from the dust clouds of endless air strikes. We have become all too familiar with such scenes in Syria, but now is the moment we must come together and say, “Enough”.

Last Saturday the security council passed a resolution for a 30-day ceasefire that would stop the bombs and allow humanitarian access. The ceasefire has barely led to a lull in the fighting. Meanwhile, diplomats in faraway capitals quibble over the timing and language of the ceasefire.

So today we say in plain terms for all humanity: the members of the security council can and must uphold the ceasefire. We cannot consign yet another promise to Syrian civilians to the rubbish bin of history nor can we accept any watered-down version of the agreement. We must act now to save lives.

Among the horrors of Ghouta, we are seeing tremendous acts of bravery: rescue workers driving towards bombs, women cooking for their entire community and doctors working around the clock with barely enough supplies. We are asking the leaders of our countries to stand with these brave Syrians and do everything in their power to uphold the ceasefire and stop the killing. When our children ask us what we did for Ghouta, let us be able to say, “Everything”.

Riz Ahmed, Sacha Baron Cohen, Isla Fisher, Sofie Gråbøl, Annie Lennox, Michael Palin, Andy Serkis, Imelda Staunton, Emma Thompson, Joe Wright

The Syria Campaign

• Natalie Nougayrède (Journal, 28 February) is too ready to castigate Europe and the US for non-intervention in the Syrian conflict. She forgets that in 2013-15 the overwhelming menace was the rise of Islamic State – not the civil war, which seemed deadlocked. Russia didn’t intervene then, but in late 2015, soon after which it pushed Isis out of Palmyra, its first significant defeat.

So “targeted air strikes” in August 2013 would have done the trick? Against whom: the Syrian government, which however authoritarian represented the vast majority of Syrian Shias, Christians, Alawites and Druze? Only major on-the-ground armed intervention could have brought a grudging end to the civil war. Would our public have tolerated so risky and unclear a venture?

Robin Milner-Gulland

Washington, West Sussex

• Join the debate – email guardian.letters@theguardian.com

• Read more Guardian letters – click here to visit gu.com/letters