By Martin Plaut
BBC Africa analyst
The Lord's Resistance Army, which has been fighting the Ugandan Government for nearly 18 years, has become know for its brutality, but the reasons for their rebellion are less well known.
The Ugandan Refugee Law Project has just interviewed 900 people from northern Uganda to try to discover just what it and its mysterious leader, Joseph Kony, stand for.
Children are abducted and forced to fight for the LRA rebels
The report says the seeds of this terrible conflict were sown in the defeat in 1986 of Presidents Milton Obote and Tito Okello by forces loyal to Uganda's current leader, Yoweri Museveni.
The remnants of the defeated forces fled north, to their home areas - fearful that the new government would carry out attacks in retribution for government massacres in the Luwero triangle under the previous regimes.
The defeated fighters reformed and eventually rallied to a spiritualist - Alice Lakewenya, in the hour of their despair.
She was in turn defeated in 1987 - and other rebels threw in the towel - leaving a power vacuum in northern Uganda.
It was this that Joseph Kony filled with the Lord's Resistance Army.
While he initially targeted government troops, he turned on civilians when the government sent civil defence militia against him.
In nearly 18 years of fighting Joseph Kony has remained undefeated. So what is his secret?
The Refugee Law Project report says his recruitment is as simple as it is bloody.
Twenty-thousand children have been abducted - often forced to kill their own parents so they have no way back.
They are used as expendable troops - frequently not even given guns to fight with.
Only 200 core combatants are fully armed with weapons supplied by the Sudanese government and other sources.
The report interviewed former LRA fighters who tried to explain Kony's philosophy.
In essence he appears to believe that his role is to cleanse the Acholi people.
He uses biblical references to explain why it is necessary to kill his own people, since they have - in his view - failed to support his cause.
Joseph Kony (r) believes he must 'cleanse' the Acholi people
"If the Acholi don't support us, they must be finished," he told one abductee.
But there are practical reasons for the war to continue.
Kony and his senior commanders live well, taking the pick of the girls they capture as wives.
They also believe that if they surrendered they would be killed by the government.
President Museveni wishes to use military means to finish him off.
But many church and traditional leaders believe that only talking can halt the LRA's murderous campaign.