This resembles the plot of "The Feeling of Power", a short story by Isaac Asimov, first published in 1958. In the story, the Terrestrial Federation is at war with Deneb:
a war of computer against computer. Their computers forge an
impenetrable shield of anti-missiles against our missiles, and ours
forge one against theirs. If we advance the efficiency of our
computers, so do they theirs, and for five years a precarious and
profitless balance has existed.
In this society the skill of doing mathematics has been lost; computers do all computations. A minor technician, Myron Aub, rediscovers the ancient art of pencil-and-paper mathematics, which they term "graphitics". This has a possibility of revolutionising the war since as well as leap-frogging the Denebian development of computers,
a missile with a man or two inside... would be lighter, more mobile,
more intelligent... A man is much more dispensable than a computer.
The story is available at the Internet Archive.