The purpose of this chapter is to provide for—

((1)) the acquisition, by purchase, lease, transfer, construction, expansion, rehabilitation, or conversion of facilities necessary for the proper development, training, operation, and maintenance of the reserve components of the armed forces, including troop housing and messing facilities;

((2)) the joint use of those facilities by units of two or more of those reserve components, to the greatest practicable extent for efficiency and economy;

((3)) the use of those facilities, in time of war or national emergency, by those units and other units of the armed forces, to the greatest practicable extent for efficiency and economy; and

((4)) any other use of those facilities by the United States, in time of war or national emergency, to the greatest practicable extent for efficiency and economy.