So the Polish intelligence selected 3 smartest mathematicians in 1929 and assigned them to the task of understanding the German encryptions. The team (Rejewski) had a breakthrough in 1932 and managed to break the Enigma codes. By 1939 they've broken many subsequent versions of the constantly upgraded ciphers.
In 1939 they gave the British: a working Enigma machine, the broken encryption, a full description of how the encryption works, how to use a machine to speed up the process (the "bomba" appliance), and what automation is needed for the following versions.
The British (Turing et al) then contributed a machine-based automation which allowed to break the following upgrades to the Enigma ciphers, which would be impractical to manual calculations.
As a side note, the Polish codebreaking bureau started with a breakthrough around 1917, when some smart soldiers managed to break Bolshevik radio communication ciphers, which allowed Poland to stop the Russian revolution's expansion by 1920 (the decisive Battle of Warsaw).
In 1939 they gave the British: a working Enigma machine, the broken encryption, a full description of how the encryption works, how to use a machine to speed up the process (the "bomba" appliance), and what automation is needed for the following versions.
The British (Turing et al) then contributed a machine-based automation which allowed to break the following upgrades to the Enigma ciphers, which would be impractical to manual calculations.
As a side note, the Polish codebreaking bureau started with a breakthrough around 1917, when some smart soldiers managed to break Bolshevik radio communication ciphers, which allowed Poland to stop the Russian revolution's expansion by 1920 (the decisive Battle of Warsaw).