Radovan Karadzic will seek to portray Bosnia's Serbs as a threatened minority that acted in self-defence throughout the war when his genocide trial resumes in The Hague on Monday.
The 1992-95 Bosnian conflict that killed 100,000 people and displaced 2.2 million "was a civil war that the Serbs did not want," Karadzic's legal adviser Marko Sladojevic told AFP.
Bosnian Serbs "merely responded to the actions of others," he said ahead of Karadzic's scheduled two-day opening statement, a summary of his defence.
The 64-year-old Bosnian Serb wartime leader faces 11 counts of genocide, war crimes and crimes against humanity before the International Criminal Tribunal for the former Yugoslavia.
Arrested on a Belgrade bus in July 2008 after 13 years on the run, Karadzic risks life imprisonment. He has pleaded not guilty and insists on conducting his own defence.
He will tell the court that Serbs found themselves "national minorities" in newly formed states as Yugoslavia disintegrated, said Sladojevic, who helped draft the statement.
Karadzic will argue that "the Muslim political side and President (Alija) Izetbegovic needed the war in order to change the status of Bosnia and achieve its final plan to establish an Islamic republic in Bosnia."
Prosecutor Alan Tieger told the tribunal last year that Karadzic was the "supreme commander" of an ethnic cleansing campaign of Croats and Muslims in the pursuit of a Greater Serbia that was to include 60 percent of the territory of Bosnia.
He is alleged to have worked with Yugoslav strongman Slobodan Milosevic, who died midway through his own genocide trial in March 2006.
"We will attack from the very start," Sladojevic said of his client's defence strategy. "We are not going to act as an ordinary defence team because ordinary defence teams think that they should only respond, always defend."
Karadzic will contend that the 1995 Srebrenica massacre, alleged to have killed more than 7,000 captured Muslim men and boys, was not genocide as charged but "at maximum, a war crime against prisoners of war."
Defence forensic experts had found evidence of 500 slain prisoners, not thousands, said Sladojevic.
"It was not a safe area as it should have been. It was never demilitarised. The Bosnian Muslims armed themselves strongly and constantly in the area and committed atrocities on the Serb villages outside the area.
"In the end, the Serb side had no choice but to eliminate the enclave militarily ... to eliminate the forces of the Muslim army."
As for the 44-month siege of the capital Sarajevo that ended in November 1995 with some 10,000 people killed, Karadzic will argue there were "dozens and dozens" of military formations in the city.
"Sarajevo was not a city of helpless civilians that were under siege," said his adviser. "The Muslims were very organised and very armed.
"Many atrocities ... were committed against their own people in order to bring about the intervention of the western powers on behalf of the Bosnian Muslims."
Karadzic boycotted the start of his trial in October last year, insisting on more time to prepare. He has sought a delay until June 17 after his opening statement, but this was refused by the court which ruled on Friday that prosecution evidence shall be heard from Wednesday, March 3.
Of 161 people indicted since the UN created the tribunal in 1993, 61 have been sentenced and two remain at large: Karadzic's military right-hand man Ratko Mladic and Goran Hadzic, former president of the self-proclaimed Serb republic of Krajina in Croatia.