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 but four million rounds were fired in the first fortnight and the 5th Army needed about trains a day to continue the battle. 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, Germany had imported nitrates for propellant manufacture and only the discovery before the war of the Haber process for the synthesis of nitrates from atmospheric nitrogen, enabled Germany to produce explosives while blockaded. Developing the process and building factories to exploit it took time. Under Falkenhayn, the procurement of ammunition and the weapons to fire it, had been based on the output of propellants, since the manufacture of ammunition without sufficient propellant fillings was as wasteful of resources as it was pointless; Hindenburg and Ludendorff wanted firepower to replace manpower and ignored the principle.