wide. German artillery was organised in a series of (barrage sectors); each infantry officer was expected to know the batteries covering his section of the front line and the batteries ready to engage fleeting targets. A telephone system was built, with lines buried deep for behind the front line, to connect the front line to the artillery. The Somme defences had two inherent weaknesses which the rebuilding had not remedied. The front trenches were on a forward slope, lined by white chalk from the subsoil and easily seen by ground observers. The defences were crowded towards the front trench, with a regiment having two battalions near the front trench system and the reserve battalion divided between the and the second line, all within of the front line. Most of the troops were within of the front line, accommodated in the new deep dugouts. The concentration of troops in the front line on a forward slope, guaranteed that it would face the bulk of an artillery bombardment, directed by ground observers on clearly marked lines. The Germans had guns and howitzers and guns and howitzers, for the simpler task of placing barrages on no man's land. Telephone lines between the German front lines and their artillery support were cut but the front line troops used signal flares to communicate with the artillery. In many places, particularly north of the Albert–Bapaume road, German barrage-fire prevented British reinforcements from crossing no man's land and parties which had captured German positions, were isolated and cut off or forced to retire. Battle French Sixth Army By the end of 1 July, the Sixth Army had captured all of the German first position except Frise on the Somme Canal. Few casualties had been suffered and had been taken. On the south bank, territorial troops buried the dead and cleared the battlefield of unexploded ammunition, as artillery was moved forward to prepared positions. I Colonial Corps had advanced within attacking distance of the German second position and indications that the Germans were withdrawing artillery had been detected. In the French had broken through on an front. The advance of I Colonial Corps created a salient and German artillery, safe on the east bank of the Somme and assisted by more aircraft and observation balloons, could enfilade the defences hurriedly built by French troops and make movement on the Flaucourt Plateau impossible in daylight. German counter-attacks at Belloy,