"Deliberate employment of weapons of mass destruction or other catastrophic capabilities, unforeseen economic collapse, loss of functioning political and legal order, purposeful domestic resistance or insurgency, pervasive public health emergencies, and catastrophic natural and human disasters are all paths to disruptive domestic shock."

Titled "Known Unknowns: Unconventional Strategic Shocks in Defense Strategy Development," the report warned that the U.S. military and intelligence community remain mired in the past as well as the need to accommodate government policy. Freier, a former Pentagon official, said that despite the Al Qaida surprise in 2001 U.S. defense strategy and planning remain trapped by "excessive convention."

"The current administration confronted a game-changing 'strategic shock' inside its first eight months in office," the report said. "The next administration would be well-advised to expect the same during the course of its first term. Indeed, the odds are very high against any of the challenges routinely at the top of the traditional defense agenda triggering the next watershed inside DoD [Department of Defense]."

The report cited the collapse of what Freier termed "a large capable state that results in a nuclear civil war." Such a prospect could lead to uncontrolled weapons of mass destruction proliferation as well as a nuclear war.

The report cited the prospect of a breakdown of order in the United States. Freier said the Pentagon could be suddenly forced to recall troops from abroad to fight domestic unrest.

"An American government and defense establishment lulled into complacency by a long-secure domestic order would be forced to rapidly divest some or most external security commitments in order to address rapidly expanding human insecurity at home," the report said.

The report said the United States could also come under pressure from a hostile state with control over insurgency groups. The hostile state could force American decision-makers into a desperate response.

"The United States might also consider the prospect that hostile state and/or nonstate actors might individually or in concert combine hybrid methods effectively to resist U.S. influence in a nonmilitary manner," the report said. "This is clearly an emerging trend."

"The aforementioned are admittedly extreme," the report said. "They are not, however, implausible or fantastical."