Three battlecruisers had been sent to South America and the brand new super-dreadnought HMS Audacious had been lost to a mine; HMS Thunderer, another super-dreadnought, was undergoing repairs.[3] German ships used three main codes for which codebooks were issued to their ships; copies had been obtained by the Entente from sunk or captured vessels unbeknown to the Germans. The British code breakers of Room 40 at the Admiralty could read German messages within a few hours of receiving them. Sufficient information had been gleaned on the evening of 14 December to know that the German battlecruiser squadron would shortly be leaving port but did not suggest that all of the High Seas Fleet might be involved.[4]