Norwegian gunman Anders Behring Breivik defended his massacre of 77 people, insisting Tuesday he would do it all again and calling his rampage the most "spectacular" attack by a nationalist militant since World War II. 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 later to explain what he meant, he compared his attacks to the U.S. atom bombs on Japan during World War II. They did it for something good. To prevent further war," Breivik said. Breivik has five days to explain why he set off a bomb in Oslo's government district on July 22, killing eight people, and then gunned down 69 others at a Labor Party youth camp outside the Norwegian capital. He denies criminal guilt, saying he was acting in self-defense, and claims the targets were part of a conspiracy to "deconstruct" Norway's cultural identity. I acted in self-defense on behalf of my people, my city, my country," he said as he finished his statement, in essence a summary of the 1,500-page manifesto he posted online before the attacks. He didn't express regret, but told prosecutors he would have preferred attacking a conference of Norwegian journalists instead of the Utoya youth camp, where most of the victims were teenagers. "Unfortunately I wasn't able to carry out" an attack against that conference, he added. Breivik's testimony was delayed after one of the five judges hearing the case was dismissed for his comments online the day after the attack that said Breivik deserves the death penalty. Lawyers on all sides had requested that lay judge Thomas Indreboe be taken off the trial, saying the comments violated his impartiality. If found mentally sane - the key issue to be decided in the trial - Breivik could face a maximum 21-year prison sentence or an alternate custody arrangement that would keep him locked up as long as he is considered a menace to society. Breivik is being tried by a panel of two professional judges and three lay judges - citizens appointed for four-year terms who participate on an equal basis in deciding guilt and sentencing. Again on Tuesday - just like the start of his trial on Monday - Breivik entered the court smirking before flashing a clenched-fist salute. Judge Wenche Elisabeth Arntzen repeatedly interrupted Breivik on Tuesday, asking him to keep his statement short. "It is critically important that I can explain the reason and the motive" for the massacre, Breivik replied.