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 In the aftermath of World War II, engineers faced challenges their slide rules couldn’t solve. Walter R. Evans wasn’t looking to change the world—he just wanted to help engineers see clearly. He ended up doing both. In 1948, Walter R. Evans gave engineers a new way to design for stability. His root locus method offered a visual approach to system behavior that engineers could learn, teach, and apply with confidence—transforming how generations approached control systems.

Into Stability tells how this breakthrough emerged in the early postwar years and spread through classrooms, companies, and the wider engineering world—long before ideas could travel at the speed of the internet.

Postwar advances in technology demanded better tools. Without root locus, the progress of control systems—and the technologies they powered—might have been slower, riskier, and harder to teach.

Clear, engaging, and grounded in personal letters and technical history, this book offers a portrait of the man behind the method: a precise thinker, a gifted teacher, and a quiet innovator whose sharp mind and sense of humor left a lasting mark on engineering.