Rumsfeld had a reputation as a skilled bureaucrat and visionary of the modern US military, according to the AP.
He served as the US Secretary of Defense in two stages, and his career spanned the tenure of four presidents.
Only Robert McNamara was the first to hold the post of US Secretary of Defense longer than Rumsfeld, who had two terms – from 1975 to 1977 under President Gerald Ford, under whom he also served as White House Chief of Staff.
He was the head of the Pentagon during the term of George Bush from 2001 to 2006.
Rumsfeld played a central role in the invasion of Afghanistan and Iraq. Before and during the Iraq war, he claimed that Iraq had an active program of weapons of mass destruction even though it was never found.
He signed decrees for the interrogation of prisoners in Iraq and the Guantanamo base in Cuba, which was essentially a green light for torturing those people.
George W. Bush replaced Rumsfeld long before US troops withdrew from Iraq.
Earlier, Bush twice rejected Rumsfeld’s resignation after photos of American staff abusing prisoners at the Abu Ghraib prison near Baghdad appeared.
Rumsfeld also oversaw the U.S. invasion of Afghanistan in 2001 with the goal of overthrowing the Taliban regime that had given refuge to al Qaeda leaders responsible for the 9/11 attacks on the United States.
Like two years later in Iraq, Rumsfeld quickly overthrew the Taliban, but failed to establish law and order or track down al Qaeda chief Osama bin Laden.
U.S. forces did not kill him until 2011 in Pakistan.
He was a close ally of Bush Vice President Dick Cheney, who worked for Rumsfeld during the terms of Richard Nixon and Gerald Ford.