Kalman's 1960 Moscow paper, not a Pontryagin/Bellman/Kelley/Bryson citation line, is the documented bridge between classical and optimal control

control-theorykalmanoptimal-controlpontryaginbellmankelleybrysonifachistory-of-technology

Stuart Bennett's history locates a genuine point of contact between classical (Nyquist/Bode) and optimal-control (Pontryagin/Bellman/Kelley/ Bryson) theory — but it is later than, and external to, all four foundational names. At the first IFAC Congress in Moscow in 1960, Rudolf E. Kalman presented "On the General Theory of Control Systems," which Bennett describes as showing "a deep and exact duality" between multivariable feedback control and multivariable feedback filtering — the mathematical move that let classical feedback-control concepts (gain, stability, filtering) be re-expressed in the state-space vocabulary of the new optimal-control theory.

This is a real, documented linkage between the two literatures, but it is Kalman's own 1960 synthesis, made after Pontryagin's 1956 maximum principle and Bellman's 1957 dynamic programming were already established, and outside the Kelley/Bryson chain the vault's claim-kelley-bryson-optimal-control-precursor traces toward backpropagation. It is the mechanism by which the two traditions were later read as related, not evidence that they were causally connected from the start — the same equivalence-vs-transmission distinction the vault's backpropagation-origins cluster keeps enforcing elsewhere (claim-recht-adjoints-equivalence-not-transmission). Kalman's own 1960 Moscow paper remains unread as a primary in the vault; whether it names Nyquist or Bode directly is an open lead, not yet a load-bearing gap for this claim, which rests on Bennett's secondary account.