Evolutionary development is based on using continuous experimentation and adaptation in changing circumstances to reward success, while allowing, but eventually eliminating, failure, Since this approach is agile, flexible, quick reacting, and thrives on change, it contrasts with strategic planning in which systems are developed in a planned and orderly fashion to meet future requirements. A planned system is rigid, slow to react, and resists or ignores change, which contrasts with how the military traditionally develops weapon systems. One word that distinguishes between evolutionary and planned development is "chaos." Chaos, like risk, is unavoidable, and hence should be managed rather than avoided. Indeed, a certain degree of chaos is desirable because it generates the necessary set of adaptations and ideas that can eventually be "selected" for evolutionary improvement. The Darwinian concept of "survival of the fittest" can be applied to ideas, systems, and organizations that seek to maintain a competitive advantage.