Hundreds of American spies during the Cold War were caught in Russia for the STUPIDEST reason
There were many secret agents during the Cold War, and they were always in danger of being caught. Both sides came up with ingenious ways of deceiving the enemy and infiltrating 'the other side.' Spies were used to acquire knowledge of what the other side was doing, but also to spread false knowledge of what was being done.
It was a highly dangerous job and many worked knowing that there was barely any chance of being rescued if caught. Prison or death by execution were the most common punishments for those unfortunate enough to make mistakes that led to their discovery.
Fake passports were the primary move for spies. Attention had to be paid to every minute detail during the forgery of a passport. Something seemingly insignificant was, however, missed by the Americans and it resulted in hundreds of American spies being caught in the USSR. Something as seemingly unimportant as staples!
The staples used in Russian passports corroded rather quickly. America, on the other hand, used stainless steel staples in the counterfeit passports for their spies. These obviously never corroded. This was a tell-tale sign for Russian officials that the passport had to be counterfeit.