Rumsfeld 's second tenure as Secretary of Defense cemented him as the most powerful Pentagon chief since Robert McNamara and one of the most influential Cabinet members in the Bush administration . His tenure would prove to be a pivotal and rocky one which led the United States military into the 21st century . Following the September 11 attacks , Rumsfeld led the military planning and execution of the U.S. invasion of Afghanistan and the subsequent 2003 invasion of Iraq . He pushed hard to send as small a force as soon as possible to both conflicts , a concept codified as the Rumsfeld Doctrine
September 11 attacks
September 11 attacks
Donald Rumsfeld