A favorite regime tactic is to drop several in sequence in order to kill or maim the ordinary Syrians who have come to help the victims of the first attack. The lucky ones, like me, who have so far avoided death are subjected to the daily terror and crippling fear of the next helicopter-borne barrage of horror.

Many of my colleagues have not been so lucky. The organization Physicians for Human Rights has documented some 233 attacks on medical facilities and more than 600 health professionals killed (97 percent of whom died, they estimate, in government-led attacks).

Human Rights Watch has documented more than 1,000 barrel-bomb impact sites in Aleppo in the year since the Security Council passed Resolution 2139, which called for an end to their use in populated areas. The Security Council, including the United States, promised “further steps” if this didn’t happen.

And yet the helicopters come. The chop-chop-chop of their blades causes panic every time. And the barrel bombs continue to rain down, on our homes, on our schools and on our hospitals, often at a rate as high as 50 per day.

Why do I stay? Because it would be strange not to: This is my city. People are being killed every day. It is my duty.

The government has recently made advances into the opposition-held areas around Aleppo, raising the specter of a siege that would have devastating consequences. Our access to the little humanitarian and medical assistance that does trickle in would be cut off. A renewed government assault on the city would put scores more Marwans on my operating table, but prevent us from receiving the medical equipment and supplies we need to save their lives.

I am a doctor and a humanitarian, not a military man: It is not for me to say how the international community should protect civilians. I only know that the bombing must be stopped by all means necessary, that the carnage must end, that civilians need a protected zone where they feel safe to go about their daily lives. The Syrian government should be held accountable for the war crimes it commits every day by using barrel bombs to kill civilians and target hospitals and schools.

The United States and the international community must look beyond addressing the Islamic State alone, or simply providing humanitarian assistance. While we work toward a political resolution of the conflict, civilians need protection now — and that requires serious American leadership.