Many of the German units on the Somme had arrived in 1914 and made great efforts to fortify the defensive line, particularly with barbed-wire entanglements to the front trench with fewer troops. Railways, roads and waterways connected the battlefront to the Ruhr, the source of material for , dug-outs underground, big enough for each, excavated every . In February 1916, following the (Autumn Battle, or Second Battle of Champagne) in 1915, a third defensive position a further back from the was begun and was nearly complete on the Somme front when the battle began. The German artillery was organised in (barrage sectors); each officer was expected to know the batteries covering his section of the front line and the batteries had to be ready to engage fleeting targets. A telephone system with lines deep back from the front line, linked the artillery.