If he could, he would be on his way right away, in his shorts and threadbare sandals. With his schoolbooks under his arm he would walk along the bumpy red road, up the hill to the gate and past the guards. And then further and further westwards.

He was already counting the days. At night he couldn't sleep a wink.

We got to know Najibu just as he was about to burst with excitement. That was in September. He was 12 years old and finally about to see his mother again. We didn't know much about him yet – he was going to tell us. His mother would also be talking to us, and of course so would the aid workers of the International Committee of the Red Cross (ICRC), without whom the story of Najibu could not be told at all.

Those people are not boastful about what they're doing. They go about their work quietly. They seek and they find. What they and their network do in the turmoil of war is a wondrous thing.

Najibu was a displaced child. Eastern Congo was his home. In autumn 2008, as battles were raging there, he fled to Uganda. He had no idea what had happened to his family, nor did his family know what had happened to him. In the chaos of war they had suddenly lost each other. When that happened, a 12-year-old was catapulted into a distant and strange world, which would sometimes be good to him and sometimes bad. At first he would inspect it like an unknown fruit and try to size up the opportunities and risks.

Najibu didn't know anything yet about all the people who would soon be on his trail. But more on that later. Najibu's story should perhaps begin with books, because they were his most precious possession. Maybe they meant less to other children in the village. What good are all those words on paper when Kalashnikovs are in command? However that may be, Najibu eagerly devoured every line of type. He had long since caught the eye of his teachers. And his mother was so proud of him. Maybe someday he would manage to escape the grip of poverty.

Later, too, in the refugee camp, he would jump at the chance to read every book he could find, like a castaway lapping up water. When he walked home after class clutching his books it looked as though he was holding on to them for support.

When Najibu fled from his village nine months before, he had no time to take any books with him. It was a November day, a cool morning. Shots suddenly flew around him, and if he wanted to stay alive he had to get going right away. He rushed across the fields. Just don't stumble! Keep going, keep going!

Rashida: where was she? He had just seen his older sister, but then she was gone, as if swallowed into the ground. He wanted to cry. He wanted to look for her. But he had no time, because the men with the Kalashnikovs were behind him. Soldiers. Or rebels. Or whoever. Najibu had to keep going across the hills. Beyond them was the border. Uganda: there he would be safe.

He had eight siblings, but none of them was anywhere to be seen now. The fighting that raged in the eastern Congo in autumn 2008 chased him ever farther from his home. It was cold and damp. He hurried on. People were running from their houses everywhere. At first he still saw some familiar faces, but as night fell they were all gone. He no longer knew anyone among those who were fleeing. He had no one to lean against, no one to offer him a word of comfort.

When the fighting began, Najibu's mother was on her way to fetch something to eat. She too had to run for her life. Later she found her daughter Rashida again. Only Najibu was nowhere to be seen. His mother thought he was dead. His face was constantly before her eyes. He looked like her father. The pert eyes had sometimes looked sulky when he had to go with her to work the fields, where he much preferred to play football.

The boy walked two whole days, always towards the east. He cut open his leg on a branch. Now that he didn't hear any more shots, burning pain was piercing his calf. The cold crept through to him under his shorts and tattered shirt. He was wearing nothing else apart from his sandals.

But still he made it to the border, and saw people in white Toyotas with "UN" in black letters. They gave him food. Finally, something to eat again. Three days later, they took him to Nakivale, Uganda's biggest refugee camp, six hours from the Congolese border.

Hundreds of thousands of families are thrust apart every year by wars and conflicts all over the world. In mountains and valleys, in deserts and savannahs, everywhere there are children like Najibu wandering alone in search of their parents. If at some point they stumble on to the Red Cross, they are very lucky. For then their names will be added to the lists of the worldwide tracing service operated by the ICRC.

Anyone who travels in Africa often runs into ICRC aid workers. They are not especially conspicuous, but they are everywhere. The Geneva-based Committee has an international mandate to come to the assistance of war victims. Its delegates look after the sick and wounded. They visit prisoners of war and detainees. They explain international humanitarian law to warring parties. And they help dispersed families to reunite. The author Hans Magnus Enzensberger dedicated a book to these people, which he entitled Krieger ohne Waffen (warriors without weapons). They have international law backing them, but nothing else.

At the ICRC base in Goma, eastern Congo: here, in simple bungalows under tall trees, the threads of the biggest tracing mission currently under way run together. Nowhere else in the world have armed conflicts separated so many people from one another in recent times. In 2008 the Red Cross collected and forwarded 88,955 messages between parents and children, brothers and sisters, husbands and wives, and detainees and their families.

This network has many faces: volunteers in villages, professional tracing personnel working for the ICRC, secretaries, drivers, mechanics, radio engineers, and people who check and supervise everything. In Goma it is the Swede Emilie Welam who does the supervising. She is a lawyer who worked in the Gaza Strip before coming to the Congo. She has so much to do these days that one has to be amazed by her calm and patience. In her office is a huge metal cabinet in which all records are stored. "We currently have about 1,000 cases to process," she said. Sometimes it is a very difficult matter to trace those who have gone missing. The work is painstaking and meticulous, and no one knows where it will lead. But Emilie has witnessed children and their parents being reunited after a long separation. That's a picture that stays with her and reminds her what she is working for.

The search carried out for Najibu began when he was photographed and registered in Nakivale refugee camp on 21 January 2009 by Red Cross personnel. He had already been in the camp for two months. He found it difficult to get used to the new surroundings. He said that at the beginning he lived all alone in a hut. The nights were hard. Every evening he was tormented by the following thoughts: were his siblings and mother still alive? He had lost his father years ago, and since then he had stuck close to his mother. He knew no one in the camp. Thousands of Congolese refugees were living there, but not a single one that Najibu had ever seen before.

Apart from his shorts, T-shirt and torn-apart sandals he didn't have anything, not even a penny in his pocket. He headed out over the hills hoping to find work. Nakivale is big. Somewhere there had to be work for him. He met Ugandan livestock breeders and boasted to them that he was good at tending goats. Would they like to see him at it? The farmers laughed, but a couple of days later he was looking after their goats. That's how he earned a little money, which he used to buy himself some soap and a shirt.

The ICRC office in Uganda forwarded the photograph of Najibu to colleagues in Goma, in the Congo. They knew from what he said that he had fled the village of Kinyandonyi, so that was where they went to look for his mother. They posted his picture on trees and notice boards, and asked for the names and addresses of relatives. Who knew Najibu? While militias and the army were fighting, there was little they could do. But there were always calmer moments – that's when the aid workers got going.

They still had not found Najibu's mother. At first she thought that Najibu was dead. She prayed for him. One day, however, she met a couple of refugees who told her they had seen her son. Where he was then, however, they could not say. Was he still alive? Now she was no longer sure, which made her even more anxious at night than before.

The mother's face betrayed the hardships of life in the remote eastern Congo. She had had to flee her own home and now, at 46 years of age, was living with her young children in a rented hut. One day a week she worked in a field belonging to the owner, who took what she reaped as rent. The rest of the week she toiled as a day labourer in the fields of other people, for one or two dollars a day. Once things calmed down again in the Congo, she would soon be able to return to her house and her own fields. Her confidence that everything would then be better was what drove her on. And if it were God's will, he would also send Najibu back to her.

On 3 March she received a visit from Ernest Bashitsi, who was wearing a blue cap with a red cross and carrying a batch of papers under his arm. Did she have a son named Najibu? Why did he want to know? Ernest pulled out a sheet of paper on which a photograph was stapled. The mother froze. It was a picture of her lost son.

She pressed the photo to her bosom again and again. Ernest Bashitsi, who had already experienced this many times, then had to fill in a form with Najibu's mother. Did she want Najibu to come home? What a question! She had to sign her name to that. This she did with a fingerprint – she had never had the opportunity to learn to read and write.

The Red Cross checked whether the woman had work and could care for Najibu, whether there would be a place for him in the school and whether medical help would be available should he fall ill. In addition to these things, calm needed to be restored to the area, which was still too dangerous to send Najibu home right away. But a beginning had been made.

The mother jealously guarded the boy's picture like a treasure. She put it in her wallet. Occasionally she pulled it out and gazed at it for long periods of time. But a few weeks later she suffered a severe blow when thieves broke into her hut and made off with everything, including the picture of her son, which had been her only comfort.

The mother sent a letter to her son, written out by the Red Cross as she had dictated. In May the messenger came to Najibu in the camp. He handed over a sheet of paper written in Swahili. "My dear child," it began. The boy sped through the 14 lines, drinking up every single word. "Thank God we received news of you and even a picture! We are well. We are still in Kinyandonyi. Your brothers and sisters send their greetings. We are all waiting for you to come home. We are looking forward so much to seeing you again. Your schoolteacher and the headmaster are also eager to welcome you back."

Fourteen lines, after six months in a camp. His mother was alive. Still, he found himself wavering back and forth. Things had improved for him in the camp. The Save the Children aid agency ran a school there, and he was among the best pupils. He was especially pleased that he was taught in English. He had learned French in the Congo, but he knew that it would be easier to find work if he knew several languages. That was one side of it. On the other side, there were many things that bothered him in the camp. He had begun living with a Congolese family, which had taken him in. But he said that the foster parents took advantage of him. The father was too strict. Najibu had to work all the time and carry water canisters that were much too heavy. "My mother never made me do that," he said.

Sometimes he tried to imagine how it would be if he were at home again for the next big festival – Christmas, when they slaughtered a cow and everyone sat together, sated, and the children could even sip a Fanta. At some point homesickness could no longer be held back. If he could, he would be on his way right away.

So it was that Najibu asked the Red Cross to take him back home. The area around his village in the Congo had become somewhat calmer, even if a lasting peace was still a long way off. The aid workers in Goma gave the go-ahead. Ugandan personnel went to Nakivale to pick up the boy and 11 other children and give them new clothing. Najibu was rebellious then. He refused to accept trousers and shoes. He grumbled a lot and appeared confused. He scoffed so much food that in the evenings he had to vomit. Elation and yearning, fear and doubt ... everything overwhelmed him.

On a sunny October morning a Red Cross car entered the Congolese village of Kinyandonyi. Najibu jumped out and ran. His mother's hut was not far away. Children came streaming out on all sides. They cheered and shouted.

But then they fell silent. Even the young ones, who had just been whining, did not make a sound. Everyone stared at the lost son. He had returned, after such a long time. And here he was, standing in front of his mother. For a moment they both seemed to freeze in place, then his mother called his name. Her voice sounded bright and clear, like a clarion blowing away all her gloomy thoughts with a single blast: "Najibu!"

The boy flung himself into her arms, and she buried her head on his shoulder as if she wanted to keep it there forever. Seconds later Najibu slipped away again and threw his hands over his face. His mother passed her hand over her cheeks. She was trembling. With the other hand she stroked Najibu's neck.

Mother and son: after all that time, all they could do was stand there. And the neighbours, who had all gathered round, did not say a word. Behind them, next to the hut, was Najibu's bag. A previous glance inside had revealed that it contained mostly books.

For the aid workers it was time to leave. Najibu was home again.