The German Army had begun 1916 equally well provided for in artillery and ammunition, massing field and heavy artillery shells for the beginning of the Battle of Verdun. Four million rounds were fired in the first fortnight and the 5th Army needed about trains a day to replace consumption. The Battle of the Somme further reduced the German reserve of ammunition and when the infantry was forced out of the front position, the need for (defensive barrages), to compensate for the lack of obstacles, increased. Before the war and the Allied naval Blockade of Germany, nitrates for explosives manufacture had been imported from Chile. Production of propellants could continue only because of the industrialisation of the Haber process for the synthesis of nitrates from atmospheric nitrogen but this took time to achieve. Under Falkenhayn, the procurement of ammunition and artillery had been based on the output of propellants, since the manufacture of ammunition without sufficient propellants and explosive fillings was pointless. Hindenburg and Ludendorff wanted firepower to replace manpower and ignored the principle of matching means and ends.