Karadzic defends Bosnian Serb 'holy' cause at trial
Mr Karadzic, who led the Bosnian Serbs during the war in the 1990s, said there was a core group of Muslims in Bosnia - then and now - who wanted 100% power.
He said the Serbs acted in self-defence after their peace plans were rejected.
He insists he is innocent of all 11 charges from the 1992-95 Bosnian war, including genocide and war crimes.
The trial had been adjourned since November and the judge rejected a new request for a further postponement.
'Mere mortal'
Mr Karadzic, 64, suspended his boycott and appeared in court along with his lawyer on Monday as the trial resumed.
"I will defend that nation of ours and their cause that is just and holy," Mr Karadzic said in translated comments at the International Criminal Tribunal for the former Yugoslavia (ICTY).
"I stand here before you not to defend the mere mortal that I am, but to defend the greatness of a small nation in Bosnia-Hercegovina, which for 500 years has had to suffer," he told the court. "We have a good case. We have good evidence and proof."
After his initial remarks, Mr Karadzic began laying out a detailed account of the events that led up to the outbreak of the war.
The wartime leader is trying to show that there was no joint criminal enterprise - no plan or plot - to carry out the genocide or "ethnic cleansing", but that Serbs were only defending themselves from perceived Muslim aggression, says the BBC's Dominic Hughes at the trial.
"Their conduct gave rise to our conduct, and that is 100% true," Mr Karadzic told the court.
'War trick'
He pointed to one defining event of the 44-month siege of Sarajevo - the 1994 attack on a market in which nearly 70 people died - saying it was a stage-managed "trick" for which Serbian forces were falsely blamed.
Mr Karadzic showed the court pictures of an empty marketplace, claiming it was the scene shortly before, as he put it, hundreds appeared and the attack was reported.
He is expected to present a two-day opening statement before prosecutors present their first witness on Wednesday.
The trial has drawn strong reactions from survivors of the Sarajevo siege.
"I don't believe The Hague can punish him enough. They should send him back to us here in Sarajevo so we can hang him here in the middle of the city," Muhamed Dizdar, a merchant in Markale market told the AP news agency.
Bloody campaign
Mr Karadzic faces two charges of genocide - including the killing in Srebrenica of more than 7,000 men and boys - as well as nine other counts including murder, extermination, persecution and forced deportation.
Prosecutors say he orchestrated a campaign of "ethnic cleansing" against Muslims and Croats in eastern Bosnia to create an ethnically pure Serbian state.
In his opening statement last October, prosecutor Alan Tieger said Mr Karadzic "harnessed the forces of nationalism, hatred and fear to pursue his vision of an ethnically segregated Bosnia".
Mr Karadzic had boycotted the proceedings, insisting on more time to prepare his case.
In November, the court appointed British lawyer Richard Harvey to take over the defence if he continued his boycott.
Mr Karadzic was arrested in Belgrade in 2008 after nearly 13 years on the run.
During his time in power, he was president of the self-styled Bosnian Serb Republic and commander of its army during the Bosnian conflict which left more than 100,000 people dead.
He is the most significant figure to face justice at this tribunal since the former Yugoslav President, Slobodan Milosevic, who died of a heart attack in 2006 before his own trial was concluded.