: Introduces Pontryagin's minimum principle as it applies to optimal control problems, framed within Hamilton-Jacobi theory.

First published in 1969 by McGraw-Hill and later reprinted by Dover Publications, Hans Sagan’s book arrived at a time when there was a distinct gap in the literature. Many existing texts were either too elementary, glossing over the rigorous "why" for the sake of the "how," or they were too advanced, buried in the dense notation of functional analysis.

Sagan interweaves the history of the subject—from Johann Bernoulli’s challenge problems to Euler’s discovery of the fundamental equation—throughout the text. This helps the reader understand why certain methods were developed, not just how they work.