The senior officials' assessment said there was a "failure to recognize, acknowledge and accurately define" the situation in which the conflicts occurred that led to a "mismatch between forces, capabilities, missions and goals," the Center for Public Integrity reported Monday on its Web site.
The Pentagon's Joint Staff, which assists the Joint Chiefs of Staff chairman, said war efforts were marked by a "failure to adequately plan and resource strategic and operational" shifts from one phase to the next.
These conclusions were in the first volume of a draft report, "Decade of War," part of a multi-volume survey of "enduring lessons" from the past 10 years of conflict.
When completed, "Decades of War" will be used by senior leaders to develop U.S. military forces for the future, Joint Staff spokeswoman Navy Lt. Cmdr. Cindy Fields said.
Fields said the May report is an internal document not available to the public, but a copy was posted Thursday on the Web site of "Inside the Pentagon," a trade publication.
While not naming those responsible, the assessment said the early dismantling of Iraq's security forces and firing of mid-level government officials -- decisions made during the George W. Bush administration -- hurt Iraq's ability to self-govern and fanned insurgency.
The report's toughest criticism was directed toward mishandling and undermanning by military commanders and political officials of key "transition" moments such as the end of major combat operations in Iraq in 2003, the renewal of Iraqi self-governance in 2004-05 and NATO's 2006 takeover of military operations in Afghanistan.
"Failure to adequately plan and resource strategic and operational transitions endangered accomplishment of the overall mission" in the first half of the decade, the report said. "Non-combat skills, to include civil affairs, had not been adequately rehearsed."
In Afghanistan, "the planning assumed that the chief duty" of international troops after 2006 would be reconstruction and humanitarian aid, which turned out to be wrong.
The reason for the error was that military planning was based on "U.S. expectations instead of those consistent with the host nation and mission," the report said.
"For example," the report noted, "the planned end-state for Afghanistan was envisioned to be a strong central government despite no record of such a government in its history and lack of broad popular support for that system of governance."