Ballistic missiles will continue to proliferate over the next few decades. More than 25 countries have ballistic missiles, but only Russia and China have intercontinental ballistic missiles. Intelligence estimates that 7,000 cruise missiles will exist by 2010. Intelligence estimates indicate that the overall likelihood of a terrorist attack in the United States involving a weapon of mass destruction (WMD) has increased. Nuclear, biological, and chemical weapons have proliferated. Information, energy, and banking networks have become increasingly tied together electronically, making cyber attacks potentially devastating. The Army has tentatively approved the "all hazards" definition for homeland security: "Protecting our territory, population, and infrastructure at home by deterring, defending against, and mitigating the effects of all threats to US sovereignty; supporting civil authorities in crisis and consequence management; and helping to ensure the availability, integrity, survivability, and adequacy of critical national assets." The definition supports land defense, response to chemical, biological, and nuclear threats, and the National Missile Defense (NMD), among other activities. At a minimum, the Army should develop a homeland security force-sizing metric for missions that would require a great deal of resources, such as the use of weapons of mass destruction or the NMD. A resource baseline capable of addressing two 10-kiloton nuclear events would enable the Army to respond to several incidents, such as one 15-kiloton event, one 22-kiloton event, or three one-kiloton events. NMD could contribute to maintaining peace by precluding a "state of concern" from using its ballistic missiles to deter the United States or its allies from intervening in a regional crisis; it also could defeat cruise missiles. The Army needs to examine two options for homeland security. One would be to add a third major theater war (MTW) to the current two MTW force-sizing metric and assign high-end missions to the Army National Guard. Another option would convert the two MTW metric into one overseas MTW and one within the United States for homeland security. Each option would cause defense planners to address homeland security as a single activity. The comparison illustrates that the two MTW force-sizing metric has outlived its usefulness. The Army should consider whether another metric would enable it to quantify its force structure requirements more accurately. In any case, the Army needs to develop a homeland security force-sizing metric. Endnotes