they were disorganised and advance to the German second line. Heavy artillery began registration and a slow bombardment on 16 July and two days of bombardment began either side of La Bassée canal as a diversion. The main bombardment was to begin at midnight on for seven hours (more rain forced a postponement). Over the final three hours, the artillery was to lift and the infantry show bayonets and dummy figures several times, to simulate an infantry advance, then the artillery was to resume bombardment of the front line to catch the German infantry out of cover. German preparations General Erich von Falkenhayn, the German Chief of the General Staff, had ordered a construction programme on the Western Front in January 1915, to make it capable of being defended indefinitely by a small force against superior numbers. An elaborate, carefully sited and fortified front position was built behind fields of barbed wire, with camouflaged concrete machine-gun nests and a second trench () close behind the front trench (), to shelter the trench garrison during bombardments. Communication trenches were built to evade Allied artillery-fire intended to obstruct the movement of reinforcements from the new rear defences. The front position was to be held at all costs as the main line of resistance but in May 1915, Falkenhayn ordered a reserve position to be built along the Western Front, behind the front position, out of range of enemy field artillery. To contain a breakthrough, the second position was to be occupied opposite a sector broken into and serve as a jumping-off point for counter-attacks. If the front line could not be recovered, the rear position could be connected to the remaining parts of the front line on either side to contain the break-in. The construction programme was a huge undertaking and was completed in the autumn 1915. The fortification programme had several opponents, notably the 6th Army commander Crown Prince Rupprecht, who claimed that a rear position would undermine the determination of soldiers to stand their ground. The front of the 6th Army had been quiet since the Battle of Loos (25 September – 14 October 1915) and in July 1916, the 6th Bavarian Reserve Division held a stretch of the front with four regiments, from east of Aubers village, north to a point near Bois-Grenier, each regiment having one battalion in the front line, one in support and one in reserve.