Children in Aleppo cannot escape their nightmares. Snipers maim and kill them in the street. Airstrikes crush them at school and at home.

Indiscriminate missiles strikes and shelling by Syrian government forces have demolished entire city blocks, killing and wounding thousands of civilians. One surgeon with the Aleppo City Medical Council performed 11 amputations on a single day in December—nothing new, except that field hospitals were seeing more of these injuries, even with infants.

Life in these field hospitals is chaotic and unforgiving. Some days, so many victims flood through the hospital door that they have to be placed side by side on the same bed. When there is no more room on the beds, they are placed on the floor. With all the operating rooms full, surgeons have to operate on the injured lying on stretchers in the hallway.

In one day, we treated three children shot in the abdomen by snipers. All of them were saved in underground operating rooms. We could not save the boy shot in the head.

We tried, unsuccessfully, to resuscitate another boy. I later learned that he had previously been declared dead at another hospital. His father brought his son to ours hoping that maybe the other doctors were wrong or a miracle could be performed.

I met a local shopkeeper who lost his home to a barrel bomb. The day I met him, a sniper shot his 8-year-old daughter in the belly in front of his shop as he stood a few feet away. Both her bladder and uterus were ruptured. She survived, but it's unlikely she'll be able to bear children.

One child I operated on had been rescued after a bomb landed near his school. The explosion blasted his forearm open. He lost all the skin on the front of his wrist and hand. His muscles were shredded, and his nerves were obliterated—an injury that will scar and disable him for life even if his hand survives.

Another child never regained consciousness after he was rescued from the rubble from an airstrike. He eventually died from his injuries in our intensive-care unit. No one knew who he was, and no one came to claim him. His body was wrapped in a white shroud, and he was taken to be buried.

On April 30, 47 people—mainly schoolchildren—were killed in an airstrike on the Ein Jalout school. Students there had gathered for an exhibition of their artwork depicting the impact of war in Aleppo.

Ein Jalout had also been bombed in August. On that day, the school had organized a charity event to donate clothes for the poor. The explosion killed and injured scores of people—mostly women and children who were volunteering. I treated one boy who had the bone fragments of his best friend embedded all over his skin. His last memory of the explosion was seeing his friend disintegrate.

No chemical weapons were involved in these attacks. Such massacres-by-other-means have become so much a part of the daily routine in Aleppo and elsewhere in Syria that they barely make headlines. Despite U.N. Security Council Resolution 2139 in February calling on all parties to cease attacks on civilians and to allow easier access for humanitarian aid, such attacks have escalated, and aid blockades have persisted.

More than 150,000 people have been killed in Syria. More than 10 million Syrians are in need of aid—about five million of them are children, according to Unicef. The flood of refugees threatens to overwhelm host countries such as Lebanon, Jordan and Turkey. After four years of conflict, no peace or cease-fire is being credibly negotiated. No resolution is being palpably enforced.

Syrian children are growing up scarred, homeless and uneducated—their families torn apart, their futures crushed. These children must not be abandoned. Aid groups and U.N. agencies can only offer humanitarian relief and medical care. Much of it goes to refugees who have managed to escape Syria. Very few of those providing aid dare to cross the border and venture to so-called hard-to-reach areas.

I cannot tell world leaders what will solve the conflict in Syria, but I ask why sustained campaigns of destruction and starvation are allowed to continue. I can only offer what I've witnessed and ask the international community not to forget about the Syrian people.

Dr. Attar is an assistant professor of orthopedic surgery at Northwestern University Feinberg School of Medicine. He volunteered in field hospitals with the Syrian-American Medical Society in Aleppo, Syria, in August 2013 and April 2014.