With many U.S. allies bracing for imminent cuts to defense budgets, and with U.S. Defense Secretary Robert Gates engaged in a campaign against profligate spending at the Pentagon, the military reserve components -- which frequently suffer disproportionately from reductions in defense spending -- might make for a tempting target. But cutting back on these crucial elements of modern Western militaries would be a mistake with significant operational consequences.
As in other countries, the U.S. military reserve structure reflects the nation's distinct historical origins, security requirements, and constitutional principles. But the U.S. Department of Defense is unique in possessing seven major distinct reserve components (.pdf) within its subordinate military departments. The Army has two reserve components: the U.S. Army Reserve and the Army National Guard. The Air Force contains two reserve components as well: the Air Force Reserve and the Air National Guard. The Navy has three reserve components: the Navy Reserve, the Marine Corps Reserve, and the Coast Guard Reserve, which falls under Navy control in wartime.
During the past two decades, the world's great military powers have come to rely increasingly on their reserve components. Previously, defense planners treated their reservists as strategic assets to be mobilized perhaps once in a lifetime, for a war comparable to World Wars I and II. Since then, these strategic reserves have become operational reserves, called up every few years -- and often several times in their careers -- as integral members of their country's "total force."