1. Simon Cameron 2. Robert S. McNamara 3. Donald Rumsfeld
I thought I was old. But you're really old. Simon Cameron predates even me.
Donald Rumsfeld was Chief of Staff to President Ford in 1974-75 during the final months of the Vietnam War after being US Ambassador to NATO for President Nixon. He was named SECDEF in October, 1975. He was appointed SECDEF again by the President George W. Bush in 2001, oversaw the defeat of the Taliban later that year and the successful invasion of Iraq and capture of Saddam Hussein in 2003. He underestimated the number of ground troops and equipment they would need during the transition to a democratic, post-Ba’athist Iraq. He preferred unmanned drone planes and “shock and awe” bombing to cut costs in the short term. These decisions cost lives, but not on the scale of what McNamara did.