Foreign Office Historians

What’s the context? Polish cryptologists reveal they have cracked the Enigma code, 26 July 1939

The three Polish codebreakers Marian Rejewski, Jerzy Rozycki and Henryk Zygalski

On 26 July 1939, in a forest near Warsaw, Polish code breakers told their British colleagues how they had cracked the German Enigma code. As war against Nazi Germany approached, the meeting symbolised the importance of political, as well as intelligence co-operation in the struggle ahead.

What’s the context? 31 March 1939: the British guarantee to Poland

Hitler and Neville Chamberlain

On 31 March 1939 Neville Chamberlain committed Britain to defending Polish independence. After years of trying to preserve peace and buy time for rearmament, he recognised that international developments and domestic opinion meant this guarantee was necessary, though it was to mean war with Germany 6 months later.