The kidnap of more than 200 Nigerian schoolgirls by hard line Islamists shocked the world - and focused new attention on the terrorist group Boko Haram.
Boko Haram is one of the most brutal Islamist insurgencies - but a Channel 4 Dispatches airing tonight (Monday 18th August at 11pm) can reveal the other side of Nigeria's war on terror.
The programme examined dozens of videos and eyewitness testimonies that show how innocent civilians are being tortured, imprisoned, even murdered by the Nigerian army and their civilian militia.
Together, they amount to powerful evidence that elements of the Nigerian state could be guilty of war crimes.
Human rights investigators say as many 4,000 people have died in military custody since the conflict escalated two years ago.
The programme includes:
Video of the bodies of dozens of young men who witnesses say were executed in cold blood by Nigerian soldiers
Videos and photographs of dozens of bodies of men who we are told died in military custody.
Video evidence of at least eleven young men being executed by uniformed Nigerian soldiers without any evidence of due process to determine whether they are Boko Haram members or not or try them for any crime. An international law expert says these appear to be summary executions, which are illegal in Nigeria and could constitute war crimes under international law
Militia members have told Channel 4 Dispatches they tie up and beat detainees to force confessions from them. An expert in international law has told us this constitutes torture and is illegal according to the Geneva Conventions
In one of the most shocking clips, a group of men described by witnesses as Nigerian soldiers and militiamen cut the throats of several young men in what appears to be revenge for the beheading of soldiers by Boko Haram
Other videos show the arrest, beating and torture of suspects before they are taken in to military custody where human rights investigators tell us hundreds possibly thousands of innocent men have died from causes including starvation, suffocation, disease and execution
Video footage – verified by a forensic pathologist - of a boy beaten unconscious by Nigerian soldiers for refusing to admit he was a member of Boko Haram. A militia member who was present at the time, says the boy died two days later
We have video evidence of civilian joint task force militia members repeatedly and severely tying up unarmed civilians suspected of being Boko Haram members. This is often done in the presence of uniformed soldiers and sometimes at joint checkpoints
Both Britain and the US continue to provide military, law enforcement, and intelligence support to Nigeria
Calls for action from the international community by a leading human rights lawyer and Amnesty International
Background to Boko Haram
Rich from oil exports, Nigeria is now Africa's biggest economy. But in the north, home to most of the nation's 80 million Muslims, people are among the poorest in the country.
It's the heartland of the brutal Islamist terror group, Boko Haram. This year alone, Boko Haram have killed over two thousand people, most of them civilians.
They portray themselves as warriors of the jihad against the West. Their name means "Western influence is a sin" - the group was originally formed to fight what they said was endemic corruption brought to Nigeria by the West.
In the past four years Boko Haram has become one of world's most savage insurgencies - beheading police officers, launching indiscriminate bomb attacks, killing school children.
Shehu Sani: President, Civil Rights Congress of Nigeria and an opposition politician says: "They [Boko Haram] burn schools like the Taliban, they kill public officials and attack military and police locations like the Taliban.... They see themselves as the Taliban of Nigeria."
Modern Nigeria was formed when its British colonial ruler forcibly united the Christian south with the mainly Muslim north.
Boko Haram is fighting for the return of an Islamic state. Their insurgency is now raging in three northern states - an area bigger than England and Wales.
Nigeria's counter-terrorism offence
In response the Nigerian military has launched a counter-terrorism offensive to try and stem the violence.
Two years ago a State of Emergency was declared in the three northern states, a joint military taskforce created, thousands of troops sent north and in August a new division created to destroy Boko Haram.
The army called its campaign "Operation Flush".
The military took control of local militias, young Muslim men who had gathered together to help identify Boko Haram members living in their communities.
Nigeria's President Goodluck Jonathan hailed this militia as "new national heroes".
Shehu Sani: President, Civil Rights Congress of Nigeria and an opposition politician says: "These are young men that have the knowledge of … the north eastern part of Nigeria so now the military can have someone by proxy carrying out their activities without them being held responsible."
The militias armed themselves with whatever was to hand – Machetes, Cutlasses, even bows and arrows. They adopted the official title "Civilian Joint Taskforce". The state government paid them salaries and some of them received basic training from members of the military.
Militia insiders admit to torturing victims
Two militia insiders agreed to speak anonymously to Channel 4 Dispatches about their activities including the use of torture to force confessions from individuals.
The militia started by setting up checkpoints in towns across the north trying to stop Boko Haram agents and infiltrators.
The militia had been given powers to detain anyone they wanted - and they started interrogating people as they saw fit.
The militia went on operations in force, moving through the countryside where Boko Haram is strongest. In their hunt for the insurgents the militia swept through remote towns and villages - even in communities where they had little local knowledge.
The Militia used these tactics in a town called Dikwa, North-East Nigeria, around the start of Ramadan 2013.
Channel 4 Dispatches have obtained video disturbing footage of torture and abuse from that operation.
The videos show the militia acting as if everyone was a potential terrorist.
Their first step was to round up the townsfolk - even their children – with threats and acts of violence.
In one video obtained by Channel 4 Dispatches a militia member tells a boy "We are going to slaughter you".
Other videos suggest little hard evidence was used to identify Boko Haram suspects.
Instead they denounced individuals on the basis of bizarre clues: thorns in the sandals from being in the bush; bruises supposedly caused by carrying guns or even a suspicious expression.
Many of the videos we've gathered show the same pattern. First, the suspects are bound.
Many suspects plead their innocence but are still threatened with a beating.
Mohammed, the militia insider, claims that this kind of treatment was the only way to get the truth.
Mohammed says: "We tie their hands and legs and place them in the sun. We beat them with a stick until they scream. Then they'll tell us everything. If he has killed someone or has a gun, he will tell us. He will tell us if he is Boko Haram. He will tell us everything."
After they had extracted confessions, the militia handed over their suspects to the Nigerian military.
'Violation of international law'
Channel 4 Dispatches showed the Dikwa videos to Mark Ellis, an international human rights lawyer, Executive Director of the International Bar Association, to see what he thought of the treatment.
Mark Ellis says:
"It is being tied tighter and tighter here. I would imagine it is difficult to breath and I imagine the pain here is beyond belief…this absolutely moves to torture, and that's prohibited.
Not only would it violate the Geneva conventions…but international human rights law."
Boy beaten unconscious by Nigeria soldiers
Abdul, the militia insider, showed Channel 4 Dispatches a video he says he filmed during a joint military and militia operation hunting for Boko Haram. He said it happened at the end of July last year in Maiduguri.
The video shows the Nigerian military directly involved in the abuse of detainees. An expert on the Nigerian military has confirmed that the uniforms are Nigerian armed forces.
Abdul said severe beatings coerced many here to agree they were Boko Haram.
The video footage –verified by a forensic pathologist – shows a boy beaten unconscious by Nigeria soldiers for refusing to admit he was a member of Boko Haram.
Abdul claims the boy died two days later
Re-living the ordeal, he says: "I think you could not bear it there for a week. We all turned into monsters as you can see."
Mark Ellis, an international human rights lawyer says: "This is one of the more egregious videos that I've seen… that's a young boy there tied up… It's quite apparent that it's military doing this… that is a war crime there because… its quite apparent military doing this and that would be absolutely a war crime."
Under international law, any alleged war crime requires an investigation by the Nigerian government. But our evidence suggests this was not an isolated incident.
Britain and the US continued support to Nigeria
After the kidnap of the Chibok schoolgirls, the world rushed to help Nigeria in its fight against the group.
Having already approved the sale of millions of pounds of security equipment over the past decade, Britain promised further assistance.
In May of this year, David Cameron said: "Today I can announce that we have offered Nigeria further assistance in terms of surveillance aircraft and a military team to embed with the Nigerian Army in their HQ …this was an act of pure evil. The world is coming together not just to condemn it, but to do everything we can to help the Nigerians find these young girls."
At the recent US-Africa Summit, President Obama promised to support the Nigerian-led efforts to combat Boko Haram. According to the statement, the US said: "We are providing an array of military, law enforcement, and intelligence support, such as counter-Improvised Explosive Device training and forensics training."
Both governments say Nigeria is a key counter-terrorism partner in the region - but what kind of partner is it?
Nigeria's military already absorbs a quarter of the nation's budget despite being dogged by constant allegations of high-level corruption.
Nigerian Army involved in wide-scale human rights abuses
At the same time our evidence indicates the army is also involved in wide-scale human rights abuses.
Nigeria has a Constitution, judiciary and Human Rights Commission to protect citizens' rights. Yet many of the videos obtained buy Channel 4 Dispatches show that in the fight against Boko Haram, summary justice is administered with no due process.
Repeatedly the videos show executions carried out with no evidence of legal process at all, in broad daylight in front of cheering crowds.
In one video, a young man was accused by the militia of illegally possessing a weapon. He is subsequently shot dead by a man in military fatigues.
In another video two men confessed to helping the insurgents but only under duress. Though they claim they were forced into it - there appears to be no room for a legal defence. A Nigerian soldier marches the men to a freshly dug grave before they are murdered.
The scale of the video evidence raises new questions about how far up the chain of command responsibility for these abuses goes.
Mark Ellis say: "Watching these videos there is a systematic nature, this is not a one off. This is evidence of something much more severe than that and the fact that the military has been seen in these videos really does begin to point to the direction of those in charge… and superiors of the military, ultimately they are responsible, as well as the state to ensure these things don't happen.
Amnesty International and Human Rights Watch concerns
Amnesty International and Human Rights Watch have passed evidence of arbitrary arrest, beatings, torture and summary executions to officials across the Nigerian government.
Amnesty International's Makmid Kamara says: "We have raised several concerns with the Nigerian army and with the Ministry of Justice and other senior officials of the Nigerian government - and we have spoken to senior Nigerian military officers who are aware of what is going on and that they have confirmed that these are things that actually happen in military and police custody.
Giwa Barracks Massacre
Despite these warnings, in March this year, a massacre occurred that appears to constitute an international war crime.
It occurred in the aftermath of the Boko Haram assault on Giwa Barracks. Hundreds of inmates escaped during the attack, running for their homes.
Amnesty International has documented that 622 people were killed by the military that day.
The government's militia rounded escapees and waited for the soldiers.
One witness saw what happened next: "They were looking for something to eat or drink. One was begging for water with his hands. All of them were crying saying they were not Boko Haram. Two soldiers came either side and asked people to move away and pop pop pop, they shot them all."
Amnesty International's Makmid Kamara says: "This is something that must be investigated by the international criminal court we think this act may constitute extrajudicial execution and crimes against humanity.
But it didn't end there. Channel 4 Dispatches obtained two horrific videos. The first video shows what we are told are the bodies of Giwa detainees being thrown into a pit. Then a Giwa prisoner is laid on the ground and his throat cut.
From what the soldiers say, it appears to be an act of revenge for Boko Haram beheading fellow troops.
A militia source told us these videos are fake. Boko Haram members have previously worn army uniforms and he says these are insurgents impersonating soldiers to discredit the army.
But evidence in the videos tells a different story. Their metadata indicates they were filmed on the same day, just hours after the Giwa break out.
The soldiers are wearing Nigerian army uniforms - on one you can see the name Operation Flush - the army's anti Boko Haram campaign. One of the weapons is marked with the number of a battalion based in the north.
And we have contacted four independent witnesses who say they recognise the man who cuts the throat - and he's a Nigerian government solider.
The same man is also seen in the second video filmed later the same day.
In the four minute sixteen second video, five men are called up, laid down in front of a pit and also have their throats cut. Other men are lined up waiting their turn.
The footage is too graphic to broadcast - but we've shown it to a forensic pathologist who has told us that these men's deaths are real.
Amnesty International says it appears these are government soldiers. They've written to the Nigerian Government seeking an inquiry.
The Nigerian military says soldiers have been impersonated before but it will investigate the videos as there is no place in the army for this kind of barbarism.
Calls for action from the international community
Mark Ellis says if these are Nigerian soldiers, the world should act: "I've been in this area of international criminal law for thirty odd years. I don't think I have ever seen anything as disturbing as this … it constitutes war crimes without question…The responsibility here is for the state of Nigeria to bring these individuals to justice and including any superior officers who condone these acts…. If there is not that type of commitment being made on behalf of the government, then this is where the international community has a responsibility to step in and put pressure on this because this is absolutely unacceptable."
Nigerian Right to Reply
The Nigerian High Commissioner in London told Dispatches we were giving in to "disinformation" and that they "dismiss the purported cases of human rights abuses and war crimes…"
"nothing of the sort is being perpetrated in Nigeria. This is because there has to be a war before you talk about war crimes. What is happening …is an effort ...to stamp out insurgency…
[where] "possible collateral damage could be experienced."
"The Nigerian Government … is a signatory to many international human rights instruments, … is doing everything possible within the ambit of law… [The] Government … or its agencies cannot be said to be targeting unprotected civilians as a matter of policy."