Three serving prisoners have been handed additional life sentences for carrying out an attack on a Bosnian war criminal in Wakefield prison.
Radislav Krstic, 62, was serving a 35-year sentence for his part in the killing of Bosnian Muslims in 1995.
Indrit Krasniqi, Iliyas Khalid and Quam Ogumbiyi, were found guilty at Leeds Crown Court of wounding with intent to cause grievous bodily harm.
Prosecutors said the men, all Muslims, were seeking revenge against Krstic.
They were already serving life terms for murder.
The trio entered Krstic's cell at the jail in West Yorkshire on 7 May last year and slashed him with blades. He suffered severe wounds to his face and neck, including a 5in (12cm) cut across his neck.
War crimes 'retribution'
As a general-major in the Bosnian Serb Army, Krstic was convicted of aiding and abetting the genocide of 8,100 Muslim men and boys in Srebrenica in 1995.
Mr Justice Henriques told the court he would have liked to extend the minimum term each defendant is currently serving, but that option was not available to him in law.
However he said the new convictions would affect their release date as it was likely their first application to the Parole Board would fail.
He told the men: "This was a crime of exceptional gravity.
"You planned an attack upon a defenceless man with an artificial leg, aged 62.
"You planned a revenge attack by way of retribution for war crimes carried out by Radislav Krstic in the 1990s.
"All three of you are practising Muslims. I have no doubt what you intended was an act of revenge for those war crimes."
Krasniqi was handed a minimum term of 12 years, with Khalid receiving 10 years and Ogumbiyi six years, to run alongside their existing sentences.
They were cleared of attempted murder.
During their trial, Julian Goose QC for the prosecution said the motive for the attack was as a "punishment or revenge".
"This was, we say as the prosecution, a planned and determined attack in which the three defendants intended to kill Radislav Krstic."
Krstic was convicted of genocide at the International Court for the former Yugoslavia, in The Hague, in 2001 and was sentenced to 46 years in prison.
An appeal court reduced the conviction to aiding and abetting genocide and his sentence was cut to 35 years.
He was transferred to the UK to serve his sentence in 2004 because the UK has a treaty obligation to take some prisoners from the War Crimes Tribunal.