The ENIGMA machine was used by the german military during World War II. They could send out messages and signals through the machine and they would automatically be encrypted and received by Morse code. The original cracking was significantly helped by operator mistakes, but other than this, the cryptographic machine was as secure as it could have possibly been.
ENIAC
ENIAC (Electronic Numerical Integrator And Computer) was originally built to help the war effort, but wasn't actually delivered to the army until shortly after the war's end. ENIAC was the first general-purpose electronic, digital computer. It was 150 feet wide, and was cited as a huge influence on designers. These photos from the US Army archives show two early programmers at work on the ENIAC.