On the streets of Liberia's capital Monrovia, the morning is a time of hope apparent. This is when the pavements swarm with children making their way to school. They sashay along, a shifting kaleidoscope of brightly coloured uniforms. Some here remember childhoods of a different stripe. They were generals, corporals and captains. They answered to names like Walking-Fucking, Frisky-Rebel and Domination. Bloody-eyed and dressed garishly for battle, they stared out insolently from magazines on news-stands across the world. They were child soldiers, both victims and perpetrators of Liberia's 14-year civil war, which ended in 2003.

This spring, global attention has been drawn once more to the use of children in war. Released in March, Kony 2012, a 27-minute film about Ugandan Joseph Kony's underage militia, has been viewed over 80 million times. In the same month, Congolese warlord Thomas Lubanga was found guilty by the International Criminal Court of recruiting child soldiers. But it was a charismatic American-educated Liberian who, back in the 1990s, perfected the practice.

On Christmas Eve of 1989 Charles Taylor, fresh from guerrilla training in Muammar Gaddafi's Libya, entered Liberia from the north with around a hundred other rebels. What started as a mission to overthrow the brutal regime of president Samuel Doe would turn into prolonged conflict between a cacophony of warring factions. Over 100,000 people were killed. Liberia became the most infamous bloodbath of the 1990s, with Taylor the pariah-in-chief.

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In 1997, a populace tired of war finally voted to give him what he wanted, making Taylor Africa's most notorious warlord-cum-president. Still peace did not come. Taylor ran the country as a personal fiefdom, looting its resources and fomenting rebellion across West Africa. Not until August 2003, with rebels approaching his mansion and the international community applying strong pressure, would Taylor finally relinquish the throne.

The recruitment of child soldiers into countless 'Small Boys Units' (SBUs) is one of numerous alleged international crimes for which he is now being prosecuted at the UN Special Court for Sierra Leone, in The Hague. On 26 April, the court's verdict is likely to make him the first African head of state to be jailed by an international court. However, thousands of the children who fought for him remain, scattered across the land they once ruled with guns. Now adults, how have they rebuilt their lives since their 'Papay', Taylor, left them?

Hidden on the seaside just off the long, straight thoroughfare that leads into the centre of Monrovia, there is a ghetto area known as 'The Old GSA'. Hundreds of demobilised combatants from all factions squatted in the derelict compound of the Government Services Agency (GSA) during and after the war. It became a vice den: joints available for five Liberian dollars (5p); girls for 150 (£1.50). On 29 February, the city mayor Mary Broh razed the whole area without warning, calling it "a toilet". It is here, amid the fresh rubble of their former homes that I meet countless young men who were Taylor's children. They are known as 'Gro-na boys' – boys who raised themselves, alone.

Alfred 'Sex' Sargbah is an articulate 31-year-old. He tells me how he was drawn into the war: "I was sitting with my grandparents when the rebels came. They picked me because I was the strongest." He speaks with pride. After a month of training, Alfred the 13-year-old was well on his way to becoming 'Sex', the rebel. I listen for regret in his voice, but hear only nostalgia.

"We were the Jungle Justice group! We could go through the bush to anywhere, on mission for Taylor. Some men would stop and cry, too tired to continue. We would just 'Boom', then bury them." He mimics the motion and sound of shooting a kneeling man.

Prince 'Small-Soldier' Kamara, now aged 28, recalls his excitement when, after being taken from his parents as an eight-year-old, he was first given a gun.

"The AK-47 was not too heavy. We f would drag it along the ground behind us. But it was the Uzi I loved. I knew it from the Chuck Norris movie Delta Force." For many child soldiers, coming from rural poverty, their weapon was the first modern tool they had laid hands on, Hollywood movies their only textbook.

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Prince can remember his first battle. "The scent of gunpowder, eyes stinging from smoke, your friend crying... it was terrible. I missed my mother at that moment. But then we captured some Nigerian peacekeepers, took them to our HQ. Then I felt so proud. People called me a big man." From then on it was easier. Prince would fight for the next 11 years.

Despite their tender ages, neither man thinks of himself as having been a "child soldier". Their talk is rather of becoming "freedom fighters", achieving adulthood by becoming a "soldier". As such, the macabre war stories of their childhoods are recounted with an absence of self-pity, and often with a sense of pride.

John 'Easy Water' Kolubah carries a permanent reminder of his violent youth. In 2002, a bullet shattered his shin bone. His lower leg was removed. He is not resentful of the injury – his rebel name Easy Water was a reference to his calm nature – but he hates the disempowerment that characterises the lives that men like he, Alfred and Prince now live. "We were soldiers. Now we are parasites: to grow, we have to live on something else. It makes me feel too bad." His injury carries a stigma. "People in big cars, they wrinkle their noses, like 'You fought for Taylor, you're crippled, you deserve it'." He looks at the ground. "We just didn't have the money to run away to America like they did."

While there is almost a total absence of formal job opportunities for the occupants of the Old GSA, not all are reliant on others. Every morning a Sierra Leonean known only as Scorpion King sets off in relentless pursuit of buried scrap metal. He plays an unlikely role in the globalised world: the scrap he unearths is transported to China on container ships, where it is used for factories and skyscrapers.

"I don't remember my given name now," he tells me. As a cousin of the notorious leader of Sierra Leone's Taylor-supported Revolutionary United Front Sam 'Mosquito' Bockarie, Scorpion King's earliest childhood memories are particularly brutal. He describes, without emotion, the process by which he and his infamous group would cut off the limbs of civilians in Sierra Leone. "Long sleeve, short sleeve," he says, running his finger across his arm first at the wrist, then at the bicep. He would later fight for Taylor in Liberia. Now, he f earns 300 to 700 Liberian dollars [£3 to £7] each day. Apart from the drug dealers, he is one of the only ex-child soldiers at the Old GSA with a regular income.

Things turned out a little differently for Roland Duo. After being taken by Taylor's rebels aged 14, he embarked on a prodigious, bloodstained rise. He became chief-of-staff of the feared Navy Marine Division, and then a key player in Taylor's lucrative import and export rackets. He is now a wealthy real estate developer, and the holder of a Master's degree.

It is 9.30pm when I am summoned to an empty bar to meet him. This 'big man' of the Liberian conflict cuts a diminutive figure in person, and offers a hand far smoother than those I grasped at the Old GSA. "There were many boy soldiers," he says softly. "But I was gifted. They were taking drugs, marijuana. My head was clear, always clear. I was only in the Small Boys Unit for two months before they saw my capabilities."

According to witnesses before Liberia's post-war Truth and Reconciliation Commission, his capabilities included the recruitment of children as young as nine, widespread looting, and overseeing violence including one massacre where over 350 civilians were hacked to death and thrown into a river. In his testimony before the body in 2008, Roland Duo denied personal involvement in any egregious human rights violations.

His explanation for how child soldiers came to fight reveals the desperate pragmatism of many caught by the Liberian Civil War. "Parents would send young ones out to look for food. I would feed them, clothe them. Sometimes they became friendly with me and my soldiers, and would follow us. We had food, you see? One might be very young but also strong." Later, I ask the man who led me to Duo to explain the logic of recruitment further. Dustine 'Trouble' Tegli is now working as a driver. He joined voluntarily as an 11-year-old in 1993, and subsequently led a 360-strong boys' militia called the 'Death Row Group'.

"Sure, I wish there was no Small Boys Unit," he says. "But you know that the next day, another armed group will drive through, and you have just left one more man that will fight against you." A general's power was almost entirely dependent on the amount of people he had under him. The bigger the group men like Tegli and Duo would marshal, the more security, the more recognition they would get from Taylor.

I ask Tegli, himself a father of two, if he harbours any regrets. He thinks f over his answer carefully. "Looking back, I would not use such profane language."

Alfred 'Sex' Sargbah, who I met at the Old GSA, wants me to meet the friend who currently looks after his 16-month-old daughter Sameria. Taweh Golafale lives with her husband in a one-room wattle and zinc house situated in another squatter community. While women were predominantly victims of the chaos, Taweh's story is less clear-cut. "It was 6 April, 1996 that I joined the war, on Broad Street, Monrovia. I was carrying a load on my head, walking with my friend. One general said, 'Hey you, put your load down, from now on you are my woman'." It was unwise to say no to a general during the civil war. But Taweh's new life with an NPFL general named 'Scorpion' turned out well. "I became used to him. I came to love him, actually, and pray for him when he went to fight."

Her friend Diana Korgbaye, another former rebel 'wife' smiles sadly. "In war-time, there's no real love." Her tale is more typical. "I was raped before I knew about those things. He forced me to be his wife." She snorts. "He had about 30." In the Liberian war, young men with the power of the gun could take their pick. Still, many women felt better off once with rebel groups. Diana followed her husband across the country, frontline to frontline, for a decade.

At the age of 16, Taweh Golafale became a general in control of Taylor's so-called 'Wives Units', taking her husband's rebel name as her own. She shows me the bluish tattoo of a scorpion on her left arm. "I did it because I saw the other people there getting so many things. You could get more food, clothing, anything you want at all. On the frontline you took your salary."

For some former child soldiers, like Starface Mannaray, the 'Disarmament, Demobilisation and Rehabilitation and Reintegration' programme, part of a post-war UN peacekeeping mission, provided practical skills and a gateway into civilian life. "'Ex-combatant' isn't written on my face," Starface tells me as he finishes repairing a rusted wheelbarrow at his roadside welding shop. But for many others, the process merely fuelled great hopes, now dashed.

Alfred Sargbah graduated from high school in 2005, and took computer classes. Still he is jobless and homeless. "Some believe that this is just how life goes. Those guys, they don't think, they just live. I can't go and dig iron, break rock. I'm an educated man and a soldier." He blames the stigma of his past for his present plight, and imagines a parallel existence untainted by war. "I see the same person I am, but parking a shining jeep, wife and children next to him. He's not more than me. He just didn't fight."

Since leaving his own life as a child soldier behind, Morlee Gugu Zawoo, Sr has devoted his life to helping people like Alfred rebuild their lives. He bounces around the central Monrovia office of the Network for Empowerment and Progressive Initiatives (NEPI), the organisation he and two other former combatants founded in 2004. He describes counselling he received in 1998 from a Lutheran church as "the turning point of my whole life... If I can have a transformation, then anyone can."

Interested in why this transformation has proved so difficult for other ex-fighters, I ask NEPI's chief trainer, Thompson Borh. He has a theory: he describes how the Liberian war caused a normal, peace-time "Community A" to be subsumed by a new "Community B". In this new community, the accepted rules and logic became the exact opposite.

"Most child soldiers quickly forgot or were never old enough to remember the rules of Community A, but became highly evolved for success in community B." The way he explains, it sounds rather like The Lord of the Flies, with Liberia the island – only the British soldier of that story never came.

The mechanic who fixes my motorcycle later that evening puts the challenge in helping ex-combatants more simply. "Can you teach a monkey not to jump?"

I'll call him Paul. A handsome man in his early thirties, he asked if I could change his name for fear of recrimination from associates of Taylor. He owns a modest house that he built for his family with the proceeds of the business he started. Nothing in his sensitive manner is suggestive of his past, which is a carefully-guarded secret. It is not until he shows me a photo of himself, in Charles Taylor's office, that I truly believe that he, too, was a child soldier.

It is hard to picture the suave young man before me fighting in Liberia's war. Paul laughs, slightly embarrassed at his past as a flamboyantly-costumed militia. "I would mark my face, put leaves all around me. It sounds crazy, but it worked. These small boys in the bush; walking, walking into bullets and looking like devils." Paul compares this masquerade to a man going to a football match. "Don't he and his friends disguise themselves, paint their faces, to act completely crazy? Then they go home and everything is normal. For some of us, it was like that."

Paul was a well-brought up boy who joined Taylor to avenge his father, flogged to death by government troops. He has never smoked, drunk, or taken drugs. "Some of us remembered that there would be a tomorrow. And that's today, you know?"

Paul doesn't deny the abject barbarity of what went on under Taylor's regime, though he is adamant the 'Chief' did not have full knowledge. He describes visiting a unit that had become cannibal. He grimaces and swallows. "I can't say why. It's war, bad things happen. You do something one time in horror, second time you feel bad, but the third time? Third time, you don't even notice."

Paul soon became part of Taylor's Special Security Service, a favoured bodyguard to the man himself. He explains the fervent devotion Taylor inspired in his child soldiers.

"It was all about his personality. He always had time. He would encourage you, always. He paid me through all my school, can you believe that? And the whole time I knew him, he never, ever appeared afraid." Paul describes "an absolute widespread feeling that Taylor was no ordinary man. That he was God-sent, blessed, a son of David."

Paul will concede that life in Liberia is better now, under president and Nobel Laureate Ellen Johnson Sirleaf. But that is his head talking. What follows comes from the heart.

"I miss him though, now, so, so badly. You have to understand, we felt there was always the future, that we, his young boys, would be able to do the things he couldn't, to change things, make them better. That's how I feel now. I feel so sad we didn't get the chance to do that for him."

As he walks me up his flower-lined drive, Paul tells me one last story. "I returned to my home village with my AK, the first time since I joined. I was 11, 12 maybe. My mother asked if she could hug me. I said no. She asked if she could shake my hand. I said she should just get me a glass of water."

Paul still takes his mother to church when he sees her, but their relationship never recovered. "That attachment, mother to son, was completely broken. The revolution did that."

I return once more to the Old GSA. The previous night, the first cough of Liberia's punishing seven-month rainy season had arrived, sending locals scarpering for cover in the dark. Makeshift shelters of tarpaulin and sticks have sprung up on its fringes. The mood is subdued as joints are passed around. A violent altercation breaks out over nothing. Prostitutes in beautiful, incongruous dresses head out to work. The Community B mentality thrives in such bleak spaces, where the world outside seems distant. Times like this see Taylor's children reminisce on the past, when they had power. They long for the return of their 'Papay' Taylor like a child does an absent, errant father.

Only the youngest among them, 25-year-old Edwin 'Bubbles' Kelly, disagrees. He was a particularly violent young killer in the Taylor government's Anti-Terrorist Unit, a blunt instrument used for Taylor's dirty work. Largely illiterate, in and out of prison ever since, his eyes are sunken, defeated.

"Taylor was a bad, bad, man. He put bad things in my mind, made me see human beings like chicken. Now just look at me."