Brazilian President Dilma Rousseff on Wednesday swore in the seven members of a truth commission created to investigate human rights abuses committed during the nation's long military dictatorship.

Rousseff, a former leftist guerrilla who spent three years in prison during the dictatorship and was brutally tortured, was moved to tears as she ushered in the long-delayed commission, whose work begins years after neighboring Latin American nations fully investigated the actions of dictatorial regimes.

"We are not moved by revenge, hate or a desire to rewrite history," Rousseff said at the ceremony in Brasilia. "The need to know the full truth is what moves us. Brazil deserves the truth, future generations deserve the truth and most importantly those who lost their friends and their families deserve to know the truth."

A study by the Brazilian government concluded last year that 475 people were killed or "disappeared" by agents of the military regime, which ruled Brazil from 1964 to 1985. A 33-year-old amnesty law has protected members of the military from being held accountable for any crimes.

The creation of the commission is marked by disagreements over the scope of its investigation.

Some commission members have said they will focus only on abuses committed by the armed forces. But retired military officers want it to also look into violations committed by leftist guerrillas who opposed the regime. Retired officers often express the opinion of the armed forces since military personnel are prohibited by law from doing so publicly.

Commission members Rosa Cardoso and Paulo Sergio Pinheiro told the O Estado de S. Paulo newspaper that the commission's main purpose is to investigate abuses committed by government agents. Cardoso is the attorney who represented Rousseff when she was imprisoned by the military in the early 1970s.

But former officers say that's not fair.

"If the commission only looks at one side ... it will be biased and its conclusion will not be impartial," retired Army general Luiz Gonzaga Shroeder Lessa told the newspaper. "What about those that were murdered by leftist militants? Don't they count?"

Former Defense Minister Nelson Jobim, who was forced from his post by Rousseff last year, said that he and the former head of the government's Human Rights Office, Paulo Vannuchi, agreed during 2010 discussions of the congressional bill establishing the commission that both the military and leftist guerrillas sides would be investigated.

"The commission is not out to punish anyone ... so it must listen to everyone," he told the Folha de S. Paulo newspaper.

Vannuchi told Folha no such agreement was reached.

"In 2010 I described the bilaterality suggested by Jobim as a legal monster," he said.

The law creating the commission does not specify who should be targeted by the investigations.

The commission, which will have two years to conclude its investigation, will not prosecute anyone because of a 1979 amnesty law that released civilians and the military from liability for politically motivated crimes committed during those years.

The Supreme Court upheld the law in 2010.

The commission will, however, reveal the abuses and the names of those who committed them.

"Just by bringing to light the human rights abuses, the truth commission is an important first step, but not a complete one because it will not bring those guilty to justice," said University of Brasilia political scientist David Fleischer.

Besides Rousseff, a number of leading figures in Brazilian politics were imprisoned, tortured or exiled during the regime. Former President Luiz Inacio Lula da Silva was briefly imprisoned for standing up to the government as a union leader. Former president Fernando Henrique Cardoso was forced into exile.

Silva, Cardoso and ex-presidents Jose Sarney and Fernando Collor de Mello accompanied Rousseff during the Wednesday ceremony.

U.S.-based watchdog group Human Rights Watch praised the move.

"The creation of the truth commission offers an opportunity for Brazil to shed light on thousands of cases of grave human rights abuses, including nearly 500 cases of forced disappearances and deaths committed during the years of military rule," the organization's executive director, Jose Miguel Vivanco, said in a letter sent to Rousseff.