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The ARCOS raid and the break in Anglo-Soviet relations, 1927

On 12 May 1927, British police raided the headquarters of the Soviet trade delegation and ARCOS (the All Russian Co-operative Society) in London, searching for top secret documents that were alleged to have been stolen from the War Office. The raid was a breach of the 1921 trade agreement with Russia, which had given diplomatic immunity to official trade agents of the USSR. Diplomatic relations between the two governments had become increasingly fraught following the election of Stanley Baldwin's Conservative government in 1924 (and the dispute over the 'Zinoviev Letter'). The ARCOS raid, and resulting fall-out, was the final straw - diplomatic relations were broken off and fears of war between the two countries increased.