Transcript for After US withdrawal, a heartbreaking look at growing humanitarian crisis in Syria
suffer this pain. Certainly not an 8-year-old child. It's three days since the artillery shell exploded, changing Sarah's life forever. How is she doing? Reporter: We're here in Syria, a country engulfed by eight years of bloody conflict. But this part of the country was largely spared until last week. Today the winds of war are howling. American troops are leaving, with a growing humanitarian crisis in their wake. Sarah's devastated family say she's only just realized the full horror of what's happened. The explosion ripped off her leg. Her little girl so fond of dressing up and posing for the camera, it's a devastating moment. Even worse, the blast killed her big brother Mohammad. He was just 13. From a hospital bed, Sarah clings to her mother. This is your brother. He was injured as well. He tried to revive his brother. Hey, hey, it's okay. You want to know what the impact of this war is? That's it. Families grieving. Kids torn apart while they're playing in the street. An entire population helpless, and abandoned. The family kept imploring us, can you help? There's no prosthetic limb, there's no treatment, they have no more money. And we're right up near the border with Turkey. This area could be occupied very, very soon. It won't be a question whether she can get anymore treatment but whether they can get out alive. It's only been ten days since president trump maid the sudden decision to withdraw Americans from the northern Syrian border. We are learning it was only 28 U.S. Troops holding the line between peace and war. That decision opened the door for Turkey to launch a military campaign against kurdish forces here. The United States is allied with both sides. Turkey is an important nato member. The kurdish military has been America's most reliable partner in the war against ISIS. They've done most of the fighting and almost all of the dying, but Turkey sees them as terrorists and vows to force them out of the area. Two years ago I was here in Syria as kurdish forces made the final push to retake the city of raqqah, the former capital of the ISIS caliphate. We're moving forward with the fighters of the ypg. These are the fighters that the U.S. Coalition is working with. They are the foot soldiers. We're moving up to their forward base. And it was here we met a young leader in the ypg, a mainly-kurdish fighting force. Her team cleared the city, street by street, building by building, death always just a step away. More than 11,000 kurdish men and women died in the war. One of them salsdar. She was killed in an ISIS ambush just hours after we left her. Her grief-stricken family left behind to mourn. We went in search of her family and found them. Hello, hello, hello. Hi. Lovely to meet you. Thank you very much. Look at this. A shrine to salsdar. She was the eldest of nine children. Her sister, Nila, a beautiful mirror image of her. Salsdar's mission is one her family is carrying on. Reporter: We showed them our "Nightline" special where salsdar was our guide on the front line. In a community, salsdar leads the fighters. Reporter: For years, he and his soldiers depended on American support and air power. Russia's now filling the void left by America, helping the Syrian military to back the kurds, who are now aligning with bashar Al Assad's regime, accused of war crimes against its own people. Reporter: They took us to salsdar's grave. Marked sehid, it means "Martyr." These are the people we met, all the other young volunteers. This young man was one helping us run through the streets to help us avoid ISIS sniper fire. What would salsdar be thinking today about what is happening right now? Reporter: Now the white house is deflecting blame and calling for a cease-fire. Our soldiers are not in harm's way, as they shouldn't be. As two countries fight over land. That has nothing to do with us. Reporter: President trump announced sanctions against Turkey on Monday. And tomorrow vice president Mike pence and secretary of state Mike Pompeo will meet with Turkey's president erdogan to broker a deal. America is simply not going to tolerate Turkish invasion of Syria any further. And we're calling on Syria to stand down, to end the violence and come to the negotiating table. Reporter: But erdogan is saying he won't sign a cease-fire. His tanks and troops now crossing the border and advancing on the Syrian city of mimbig. But graphic footage shows some offshoots of Al Qaeda. Like the death of a leader who was dragged from her car and shot 23 times. If verified, this is a war crime. As is the targeting of civilians. The kurdish military gave us this video of a convoy packed with people they say was hit by a Turkish airstrike. Bodies and lives shredded in an instant. My friend from the bbc's just said that all pulling out toward the border right now. I think we need to leave. The line between allies and enemies is moving dangerously fast, but not everyone has the option to seek safer ground. This is personal. This is, these are people you know. These are neighbors. These are friends. And you don't get to leave. This is my job. I will just stay here. I didn't tell my parent that I'm here, because they will be so afraid. Reporter: Do you have a plan? We don't have any plans. Reporter: Neither does the family of that little girl in the hospital who lost her leg. Sarah's father says he wants to leave their shattered home and the neighborhood that used to be safe. But there's nowhere to go. Thank you, sir, I'm so sorry. You're in the middle of this part of the world in the middle of all this and someone comes out and office you hospitality. The next is on keeping Sarah alive, distracting her from the pain. Because the youngest suffer the most when men make war. For "Nightline," Ian Pannell in northern Syria. Our thanks to Ian and his team on the ground for that harrowing report.
This transcript has been automatically generated and may not be 100% accurate.