Rumsfeld to Diane Sawyer: 'It's Possible' Troop Decisions Were a Mistake in Iraq

Feb. 7, 2011— -- More than four years after leaving public life, former Defense Secretary Donald Rumsfeld continues to believe the war in Iraq was worth the effort, and has no apologies for his decision-making in leading the campaigns in Afghanistan and Iraq.

In an exclusive interview with ABC's Diane Sawyer, Rumsfeld concedes that "it's possible" that decisions on how many troops to send into Iraq marked the biggest mistake of the war.

"In a war, many things cost lives," Rumsfeld told Sawyer.

Pressed on the fact that President Bush has written that cutting troop levels in Iraq was "the most important failure in the execution of the war," Rumsfeld called that "interesting."

"I don't have enough confidence to say that that's right. I think that it's possible. We had [an] enormous number of troops ready to go in. They had -- we had off-ramps, if they weren't needed."

"It's hard to know," Rumsfeld continued. "You know, the path you didn't take is always smoother."

Watch Diane Sawyer's Exclusive Interview With Donald Rumsfeld on ABC's "World News With Diane Sawyer" on Monday, Feb. 7, on "Nightline" That Evening, and Feb. 8 on "Good Morning America" and "World News."

The interview -- Rumsfeld's first for television since 2006 -- is tied to the publication of his memoir, "Known and Unknown," this week.

The book spans a half century that took Rumsfeld, now 78, from a back bench as a 30-year-old member of Congress to success in the private and public sectors. He served Republican presidents from Richard Nixon to George W. Bush, including a stint as President Gerald Ford's chief of staff.

Remarkably, he would become both the youngest and oldest man to have served as secretary of defense -- tenures separated by 24 years.

The interview covers the range of Rumsfeld's tenure as Bush's secretary of defense, including harsh interrogation tactics he authorized for use against suspected terrorists, and the scandal at Abu Ghraib prison in Iraq that Rumsfeld himself has described as the low point of his time at the Pentagon.

Reminded in the interview that another former Defense secretary, Robert McNamara, famously said of Vietnam years after the war that "we were wrong, terribly wrong," Rumsfeld rejected the comparison.