"Although proportional navigation was apparently known by the Germans during World War II at Peenemu¨nde, no applications on the Hs. 298 or R-1 mis- siles using proportional navigation were reported [2]. The Lark missile, which had its first successful test in December 1950, was the first missile to use pro- portional navigation. Since that time proportional navigation guidance has been used in virtually all of the world’s tactical radar, infrared (IR), and television (TV) guided missiles [3]. The popularity of this interceptor guidance law is based upon its simplicity, effectiveness, and ease of implementation. Apparently, proportional navigation was first studied by C. Yuan and others at the RCA Laboratories during World War II under the auspices of the U.S. Navy [4]."

From Tactical and Strategic Missile Guidance Sixth Edition.

(To preempt the confusion. Proportional navigation isn't a simple P controller, the missile is seeking an intercept path)

>Not silly at all if you haven’t invented microcontrollers yet.

Apparently the Germans did try that during WW2, but such a missile can not be effective, outside of e.g. bomber intercept.

The "magic" of the AIM-9 Series is that it could achieve this without micro controllers.