Of related interest, here is an old CIA.gov webpage giving an account (from the CIA, keep in mind..) of the United States' realization that the Soviet Union was

Of related interest, here is an old CIA.gov webpage giving an account (from the CIA, keep in mind..) of the United States' realization that the Soviet Union was building the Alfa class of submarine with titanium hulls, which many people believed wasn't possible for various reasons (the difficulty of shaping and welding huge pieces of titanium in dirty shipyards, titanium alloys supposedly dissolving in sea water, etc): https://web.archive.org/web/20080919231406/https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/csi-studies/studies/vol52no3/unravelling-a-cold-war-mystery.html https://web.archive.org/web/20080919231406/https://www.cia.g...