This text is intended for structural, mechanical, and optical engineers who wish to obtain an understanding of the principles of strength determination for optical components. Those who work with ground-, air-, or space-based systems, as well as with ceramics, semiconductors, and the like, will gain an understanding of fracture mechanics applications. This text expands basic fracture mechanics theory to include residual stress, which is rarely reported on in the literature and can have dramatic effects on lifetime. While complex equations are presented and a basic understanding of engineering principles is necessary, complex knowledge of fracture mechanics and energy principles is not required.