This program uses coupled theoretical and experimental approaches to examine strategies to solve the “conflict” of overcoming the traditional compromise between hardness vs. ductility which limits the attainment of strength and toughness as a vital requirement for structural materials. It emphasizes advanced metallic alloys by focusing on the interplay between the individual mechanisms that contribute to strength and toughness, that of plasticity and crack-tip shielding, noting that these phenomena may originate at different structural length-scales. The central objective is to seek a fundamental understanding, at atomistic to near-macroscopic length-scales, of the scientific origins of damage-tolerance in primarily single-phase, multi-element metallic alloys. The ultimate aim is to uncover the relationships between atomic-scale phenomena and the macroscopic mechanical behavior of structural metallic materials.