a (preliminary bombardment) which ceased as the infantry began the assault. A moving barrage of fire was proposed as a combination of both methods and became a standard practice later in the war as guns and ammunition were accumulated in sufficient quantity. Falkenhayn issued memoranda on 7 and 25 January 1915, defining a theory of defensive warfare to be used on the Western Front, intended to enable ground to be held with the fewest possible troops. By economising on manpower in the west, a larger number of divisions could be sent to the Eastern Front. The front line was to be fortified to enable its defence with small numbers of troops indefinitely and captured ground was to be recovered by counter-attacks. A second trench was to be dug behind the front line, to shelter the trench garrison and to have easy access to the front line, through covered communication trenches. Should counter-attacks fail to recover the front trench, a rearward line was to be connected to the remaining parts of the front line, limiting the loss of ground to a bend () in the line, rather than a breakthrough. The building of the new defences took until the autumn of 1915 and confronted Franco-British offensives with an evolving system of field fortifications, which was able to absorb the increasing power and sophistication of breakthrough attempts. During the mobile operations of 1914, armies operating in hostile territory had relied on wireless communication to a far greater extent than anticipated, having expected to use telegraph, telephones and dispatch riders. None of the armies had established cryptographic systems sufficient to prevent eavesdropping and all of the armies sent messages containing vital information in plain language. From September–November, the British and French intercepted messages, which showed the disorganisation of the German command in mid-September and the gap between the 1st and 2nd armies on the eve of the Battle of the Marne. Similar plain language messages and the reading of crudely coded German messages, gave warnings to the British of the times, places and strengths of eight attacks by four German corps or more, during the Race to the Sea and the battles in Flanders. Casualties By the end of the battles at Ypres, German army casualties in the west were including The French army casualty total from was which, with losses of from gave a total of by the end of the year.