Roughly half of the Army's combat forces at the end of 2005 were so-called heavy units-forces that are equipped with armored vehicles and that provide significant firepower. To support those units, the Army maintains a fleet of approximately 28,000 armored vehicles. Now that the Cold War is over, some defense experts have questioned the relevance of such vehicles to the current national security strategy and their continued usefulness (notwithstanding their contributions to recent operations, such as Desert Storm and Iraqi Freedom). The average age of the armored combat vehicle fleet at the end of 2005 was relatively high, and the fleet comprises vehicles designed several decades ago. Moreover, units equipped with the vehicles in the current fleet are too large and too heavy to be moved overseas easily and quickly by the Air Force's C-17s, the most numerous of its long-range transport planes. For all practical purposes, heavy units must be transported overseas by ship-a process that takes weeks. In today's environment of rapidly evolving conflicts, the Army's goal is to have units that have the combat power of heavy units but that can be transported anywhere in the world in a matter of days. To address concerns about the armored vehicle fleet's aging and the difficulties involved in transporting it-as well as to equip the Army more suitably to conduct operations overseas on short notice using forces based in the United States-the service created the Future Combat Systems (FCS) program in 2000. A major modernization effort, the program is designed in part to develop and purchase vehicles to replace those now in the heavy forces; the new vehicles would be much lighter, thereby easing the deployment of units equipped with them. But the FCS program, poised to develop a total of 18 new systems (including eight manned vehicles to replace those in the Army's current armored fleet) and a network to connect them all will not field any new vehicles until December 2014 at the earliest. Furthermore, because those new vehicles will be expensive, the Army plans to buy relatively small quantities of them each year. As a result, the armored vehicles now in the Army's combat units will not all be replaced by FCS components until after 2035, a prospect that has evoked concerns about the costs of maintaining those older vehicles and upgrading them to prevent their becoming obsolete. In addition, questions have been raised about the FCS program's technical feasibility and affordability. Some experts doubt that the Army can develop and test the necessary technologies in time to start producing lightweight manned vehicles by 2012-a requisite for meeting the deadline to field them according to the Army's current schedule. Another concern is funding for the quantities of FCS equipment that the Army is now planning to buy. Any reduction in the FCS procurement rate would force the Army to retain its already aging armored vehicles even longer and to invest more funds in their maintenance.