Reading a prepared statement in court, anti-Muslim extremist Anders Behring Breivik lashed out at Norwegian and European governments for embracing immigration and multiculturalism.
He claimed to be speaking as a commander of an anti-Islam militant group he called the Knights Templar, a group that prosecutors say does not exist.
Maintaining he acted out of "goodness, not evil" to prevent a wider civil war, Breivik vowed, "I would have done it again."
Pressed by prosecutors to explain what he meant, he compared his attacks to the U.S. dropping atomic bombs on Japan during World War II.
"They did it for something good, to prevent further war," Breivik said. "The attacks on July 22 were a preventive strike."
"I acted in self-defense on behalf of my people, my city, my country," he said as he finished his statement, essentially a summary of the 1,500-page manifesto he posted online before the attacks.
"I therefore demand to be found innocent of the present charges," he said.
He compared Norway's Labor Party youth wing to the Hitler Youth and called their annual summer gathering an "indoctrination" camp.
But he later told prosecutors he would have preferred attacking a conference of Norwegian journalists instead, but wasn't able to carry out that "operation."
Families of the victims were upset at his testimony.
"I think it's important to underline that we don't view Breivik as a politician in this matter. He is a mass murderer," Trond Henry Blattmann, whose 17-year-old son was killed on Utoya, said outside the court.
Even his lawyers concede Breivik's self-defense claim is unlikely to succeed and said the main thing for them was to convince the court that Breivik is not insane.
One official psychiatric examination found him legally insane while another reached the opposite conclusion. The judges panel will decide whether to send him to prison or compulsory psychiatric care.
During his testimony Tuesday, Breivik rejected suggestions that he has a narcissistic personality disorder.