The "two war" strategy that has underpinned U.S. military planning for the past decade has outlived its usefulness, leaving the United States increasingly vulnerable to emerging threats like ballistic missiles and cyberattack, Defense Secretary Donald H. Rumsfeld told Congress.
Rumsfeld Calls U.S. Defense Strategy Out of Date
(Posted on 06/23/2001)
One problem with the "two war" strategy is that we've never been willing to pay for the forces that would actually be required to fight two major wars at once. The other problem is that the two-war strategy actually boiled down to strategy and forces to fight two very particular wars (Iraq and Korea), while the real-world crisis responses we did were all over the damn place. Some of our initial fumbling in Afghanistan was due to the mismatch of forces and strategy this caused.