The history of tubes. We went to school and worked on some of the last tube based operational digital electronics in the world. Devices designed to allow us to destroy this planet of most living things in case of a first strike on the then superpowers.

Devices with hundreds of tubes designed to take EMP hits from MT sized nuclear bombs and still keep running. Devices that are still classified today because of what the did, even after the technology was long obsolete. Keys were stolen by POS criminals but the actual device was never broken.
https://jproc.ca/crypto/kwt37_aux.html

https://en.wikipedia.org/wiki/Vacuum-tube_computer