A Syrian civil defence volunteer, known as the White Helmets, holds the body of a child. (Ameer Alhalbi/AFP/Getty Images)

Samer Attar, a surgeon with Northwestern Medicine in Chicago, is a volunteer with the Syrian American Medical Society and the Aleppo City Medical Council.

Aleppo is a resilient city, rich in history, older than New York, Paris and London. It is not a city of terrorists. It is a city full of ordinary people living everyday lives, people who want to put food on the table, send their kids to school and keep their families safe, just as anyone else in the world would want for their family. But its streets are literally flowing with blood.

How can the world sit idle as the Syrian government, aided by Russia and Iran, brutalizes the people of Aleppo?

I saw this carnage for myself when I volunteered in an Aleppo field hospital in July. I was the last American to leave before Syrian government forces encircled and besieged the city.

On my first day, I saw a young mother newly paralyzed when a “barrel bomb” landed on her home. Her family pulled her from the rubble and brought her to the hospital. They were covered in blood and dust. As a last-ditch effort, Aleppo’s only neurosurgeon attempted to open her spinal canal to relieve pressure on her spinal cord, but it didn’t work. She would never walk again.

Next to her was another young mother on life support. A barrel bomb struck her home as well, killing her son and daughter. She had been pregnant, and the blast also killed her fetus. Her husband was working at his shop across the street. When he ran home after the first bombing, a helicopter dropped a second bomb that sent shrapnel into his head. Both father and mother survived, left only with scars and dead children.

On it went. The next two weeks were darker and more brutal. I saw human bodies dismembered, burned, crushed, ripped open, cut in half.

By my last day, I was doing one surgery per hour. Then a driver risked his life to transport a few of us out on the Castello Road, the last supply route into Aleppo. Syrian government forces later permanently cut the road and besieged eastern Aleppo.

Since then, unbelievably, things have gotten worse.

Aleppo has been pummeled with barrel bombs, chlorine gas bombs, cluster bombs, bunker-busting missiles and even napalm. The hospital where I worked was so severely damaged by bombardment this past week that it is now out of service.

“In one day, we received 180 wounded civilians, including 72 children and 36 women. Many of them were critically injured,” Mohamed Abu Rajab, a nurse with the Syrian American Medical Society, reported in September. “We had people dying in the ERs. Someone died because we couldn’t get to him in time to save his life. The floor was overflowing with injured and blood.”

The U.S., British and French air forces are already over Syria. Why do they do nothing to stop the government’s attacks on homes, schools and hospitals? In their inaction, they have essentially green-lighted the war crimes of the Syrian government and its allies.

With every war crime, the Assad government grows emboldened to do worse. The Syrian and Russian governments’ actions are as much of a threat to world peace and security as the Islamic State. The bombs they drop kill innocent civilians and are radicalizing rebel forces.

President Obama and Secretary of State John F. Kerry speak of pleas and diplomacy. Why has it been so hard for them to see that they have been negotiating with thugs who laugh at their fecklessness? Since when does the United States plead with war criminals?

How will Obama and the leaders of the world’s powers explain themselves 10 years from now, when they look back and say that they did nothing?

Experts who have never set foot inside Syria say nothing can be done. I welcome them to spend one day volunteering in any Syrian field hospital amputating children’s limbs. I encourage them to spend one day with the White Helmet rescue workers digging with bare hands through the rubble for survivors as helicopters drop bombs on them. Then see if they still say nothing can be done.

This is not a call for a U.S.-led invasion of Syria. It is simply a call to protect civilians and the medics who are trying to save them from Bashar al-Assad’s air force. With or without Russia, the United States and its allies must enforce U.N. Security Council resolutions — by grounding the Syrian air force, destroying runways and airfields if necessary, demanding an end to humanitarian sieges and implementing a global response if the Syrian government refuses. There can be no meaningful cease-fire or political solution as long as Syrian jets and helicopters rain hell from the skies.

The Holocaust, Cambodia, Bosnia, Rwanda, Syria. The genocide of our time keeps getting shoved out of sight and out of mind, but enough is enough.

President Obama still has a chance to stand up for the Syrian people.