Donald Rumsfeld dead at 88: Former Defense Secretary who oversaw Iraq and Afghanistan wars passes away

, an American statesman and devoted husband, father, grandfather and great grandfather," it read.

"History may remember him for his extraordinary accomplishments over six decades of public service, but for those who knew him best and whose lives were forever changed as a result, we will remember his unwavering love for his wife Joyce, his family and friends, and the integrity he brought to a life dedicated to country."

Regarded by former colleagues as equally smart and combative, patriotic and politically cunning, Rumsfeld had a storied career under four presidents and nearly a quarter century in corporate America.

In 2001 he began his second tour as Pentagon chief under President George W. Bush, but his plan to "transform" the armed forces was overshadowed by the September 11 terrorist attacks.

He oversaw the US invasion of Afghanistan and the 2003 overthrow of Saddam Hussein in Iraq, where he was blamed for setbacks including the Abu Ghraib prisoner abuse scandal and for being slow to recognize a violent insurgency.

He was fired by President George W Bush in 2006 with US troops bogged down after three-and-a-half years of fighting in Iraq.

In his memoir, "Known and Unknown," Rumsfeld discussed his entire life, including his six years as Bush's defence chief.

Speaking out for the first time since leaving office, Rumsfeld offered a vigorous explanation of his own thoughts and actions about the war and is making available on his website many previously classified or private documents.

Much of Rumsfeld’s explanation of what went wrong in the crucial first year of the occupation of Iraq stems from a pre-war failure to manage the post-war political transition when the State Department and Pentagon held vastly different views.

Rumsfeld depicted Bush as presiding over a national security process that was marked by incoherent decision-making and policy drift, a detriment to the war effort.

He suggested that Bush was at fault for not doing more to resolve disagreements among senior advisers.

Bush "did not always receive, and may not have insisted on, a timely consideration of his options before he made a decision, nor did he always receive effective implementation of the decisions he made," Rumsfeld wrote.

Addressing charges that he failed to provide enough troops for the Iraq war, the former defence chief wrote: "In retrospect, there may have been times when more troops could have helped."

But Rumsfeld insisted that if senior military officers had reservations about the size of the invading force, they never informed him.

In a lengthy section on the administration’s treatment of wartime detainees, Rumsfeld said he regretted not leaving office in May 2004, after the Abu Ghraib prison scandal erupted.

"Looking back, I see there are things the administration could have done differently and better with respect to wartime detention," Rumsfeld acknowledged.