WASHINGTON (ABC News) -- In a wide-ranging speech at the National Defense University, in Washington D.C., today, President Obama launched a spirited defense of his administration's efforts to pursue terrorists overseas, even while he outlined a more limited path forward in the fight against terror.
"We are at war with an organization that right now would kill as many Americans as they could if we did not stop them first. So this is a just war -- a war waged proportionally, in last resort, and in self-defense," Obama said. "And yet as our fight enters a new phase, America's legitimate claim of self-defense cannot be the end of the discussion."
In the first major foreign policy address of his second term, Obama addressed head-on some of his administration's most passionate critics from both the opposite end of the political spectrum and his own party.
"These are tough issues and the suggestion that we can gloss over them is wrong," Obama said when a protester repeatedly interrupted his hourlong remarks.
Obama said that on Thursday he signed a Presidential Policy Guidance that outlined not only his administration's guidelines for the use of force against terrorists but for more oversight and accountability for those actions.
He called on Congress to close Guantanamo Bay, and he encouraged the use of diplomatic power to address the ideology that produces terrorists domestic and abroad.
Yet in the speech, Obama insisted that his administration's strategies were proactive and effective, despite questions about the legality of some of the actions.
He spoke pointedly about intelligence gathered in Osama bin Laden's compound that proved that al Qaeda operatives knew that drone strikes were working.
"In the intelligence gathered at bin Laden's compound, we found that he wrote, 'We could lose the reserves to the enemy's air strikes. We cannot fight air strikes with explosives.' Other communications from al Qaeda operatives confirm this as well," Obama said. "Dozens of highly skilled al Qaeda commanders, trainers, bombmakers and operatives have been taken off the battlefield. Plots have been disrupted that would have targeted international aviation, U.S. transit systems, European cities and our troops in Afghanistan."
"Simply put, these strikes have saved lives," Obama said.
He also acknowledged that drone strikes have resulted in civilian deaths and, like in any conflict, may have had a negative impact on public perceptions of the U.S. abroad. But Obama said that the strikes, and the civilian casualties that they have resulted in, are preferable to the alternative.
"To do nothing in the face of terrorist networks would invite far more civilian casualties," Obama said. "Let us remember that the terrorists we are after target civilians, and the death toll from their acts of terrorism against Muslims dwarfs any estimate of civilian casualties from drone strikes."
Ahead of Obama's speech, Attorney General Eric Holder on Wednesday disclosed publicly for the first time that four American citizens had been killed in drone attacks.
The administration says that only one of these people, Anwar al-Awlaki, a senior al Qaeda official, was targeted. One of the other three was killed with al-Awlaki; another was al-Awlaki's son, killed in another strike.
Obama said that he does not believe the U.S. government can target and kill American citizens without due process, but that American citizenship cannot be used as a "shield."
"His citizenship should no more serve as a shield than a sniper shooting down on an innocent crowd should be protected from a SWAT team," Obama said. "That's who Anwar al-Awlaki was, he was continuously trying to kill people."
The revelations come at a time when the U.S. has already begun drawing down the number of drone attacks it carries out, which a senior administration official said today is partially a result of a monthslong process of refining the requirements for carrying out a strike.
Obama's liberal allies have also not forgotten his 2008 campaign promise to close Guantanamo Bay.
Obama said that he remains committed to closing the facility but he urged Congress to repeal its restrictions on transferring detainees away from the prison, and he called on lawmakers to close it.
"No person has ever escaped from one of our super-max or military prisons in the United States-- ever," Obama said. "Given my administration's relentless pursuit of al Qaeda's leadership, there is no justification beyond politics for Congress to prevent us from closing a facility that should never have been opened."
But, speaking with ABC News, Andrea Parsow, senior counterterrorism counsel at Human Rights Watch, said that by not moving immediately after taking office to close Guantanamo, Obama may have missed his window in 2008 when there was some bipartisan support for closing the prison.
"I think he was convinced by his advisers that doing so would be a politically risky move at the time. But by not acting, he opened up the space to make things like closing Guantanamo political," Parsow said.
With pressure to close the prison mounting, critics of the administration are unlikely to be satisfied by today's speech.
For more than 100 days, prisoners at Guantanamo Bay have been on a hunger strike and some are now being fed through tubes, which has only further outraged opponents of the prison.
In the speech, Obama also addressed two scandals that have dogged the administration, particularly in the past several weeks: the attack on a U.S. consulate in Benghazi, and reports that the Justice Department seized phone records of several journalists in the course of investigating leaks of classified information.
Obama reiterated his pledge to implement the recommendations of the Accountability Review Board, which found "unacceptable failures" in Benghazi. And he also expressed concerns that the Justice Department's investigation of leaks may have gone too far.
"I am troubled by the possibility that leak investigations may chill the investigative journalism that holds government accountable," Obama said. "Journalists should not be at legal risk for doing their jobs. Our focus must be on those who break the law."
The speech featured a litany of items Obama would like added to Congress's agenda, from repealing the "authorization to use military force" (signed into law just after 9/11 and authorizing the use of the armed forces against those responsible for the attacks) to the closing of Guantanamo Bay.
But at the same time, little time remains before Obama is perceived as a "lame duck," effectively limiting the amount of sweeping policy he can affect from the Oval Office.
"If you're going to get anything done in your second term it's really got to be in the first year, because the next year is an election year. That's what's really dictating it," said Larry Korb, a senior fellow at the Center for American Progress and a former assistant secretary of defense in the Reagan administration.
Obama has also faced mounting pressure on both sides of the political aisle to explain the U.S.'s policy around drone attacks and when he believes the government is justified in targeting U.S. citizens.
In March, Republican Tea Party-backed Sen. Rand Paul (R-Ky.) filibustered CIA Director John Brennan's confirmation hearing for 13 hours to protest the U.S. drone program.
And on Wednesday, the human rights group Amnesty International, released a new report blasting the administration's drone program for perpetrating executions in violation of international human rights law.
By laying out publicly his administration's policy for the future of the war on terror at the onset of his second term, Obama may be looking to solidify his presidential legacy.
"I think when it comes to the drone program and the future of the war against al Queda, he's thinking of what he wants to leave in place for the next president," Parsow said. "He's a young man; he's going to have a lot of years to look back on what he has wrought."