From intelligence obtained by traffic analysis of German radio signals, the British had concluded that major German warships were about to put to sea; Ultra intelligence obtained by breaking German codes did not provide any information on Operation Berlin as the British were unable to decrypt the codes at this time. On 20 January the Admiralty warned the Home Fleet that another German raid was likely. Tovey immediately dispatched two heavy cruisers to reinforce patrols between Allied-occupied Iceland and the Faroe Islands. On 23 January the British naval attaché in Sweden passed on a report from agents in Denmark that the German battleships had been sighted passing through the Great Belt. This intelligence was provided to Tovey during the evening of 25 January.