http://www.carlisle.army.mil/usawc/P...inter/gray.pdf

Notice footnote 18:

Secretary of Defense Robert M. Gates offers the contestable statement that "[f]or the foreseeable future, this [strategic] environment will be defined by a global struggle against a violent extremist ideology that seeks to overturn the international state system." National Defense Strategy (Washington: Department of Defense, June 2008), 2.