During the invasion of Poland (1939) the Polish codebreakers were sent to France for safety. Later, they fled to Britain. Making technical improvements, British codebreakers solved a vast number of messages from Enigma, and gave the plaintext to military staff. The information got from this, called "Ultra" by the British, was a great help to the Allied war effort. Ultra also included decrypts of other German, Italian and Japanese cyphers and codes, including the cypher of the German High Command.