This is a ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD report procured by the Pentagon and made available for public release. It has been reproduced in the best form available to the Pentagon. It is not spiral-bound, but rather assembled with Velobinding in a soft, white linen cover. The Storming Media report number is A222923. The abstract provided by the Pentagon follows: An improved rolled homogeneous armor (IRHA) steel with enhanced ballistic performance has been developed. Increases in ballistic performance are attributed to higher hardness levels achieved by IRHA, which maintain adequate toughness and ductility. Through augmentation of a generic chemical composition for standard rolled homogeneous armor (RHA) material, and optimization of heat treatment, greater hardenability, and higher hardness levels were attained. The higher hardenability ensures that through-thickness hardness, with the desired martensite microstructure, is obtained for armor plates up to 3 in thick, using current steel mill facilities and practice. The optimal, relatively low-carbon, nickel-chromium-molybdenum (Ni-Cr-Mo) IRHA alloy was developed in-house, employing U.S. Army Research Laboratory (ARL), Materials Directorate (MD) laboratory facilities, followed by steel mill production heats demonstrating scale-up and producibility. Ballistic testing vs. projectiles, ranging from medium caliber to tank rounds, established that the IRHA material at the HRc 40 hardness level is best suited for vehicle hull applications, while material at HRc 48 provides better protection as applique armor. The armor plate at both hardness levels (HRc 40 and 48) demonstrated structural integrity upon high kinetic energy (KE) ballistic loading, through passing the required full-scale 105-mm armor piercing (AP) T182 projectile impact tests. At the HRc 40 level, the IRHA weldability and fabricability were shown to be comparable to standard RHA for tank construction.