On the left flank, the British XII Corps with the 22nd and 26th divisions, reinforced by the Greek Serres Division was to attack the difficult Pip Ridge. The British concentrated 231 pieces of artillery, including heavy 8-inch howitzers. The bombardment took place over two days, included gas shells and concluded with a rolling barrage, behind which the infantry was to advance. The British spent the time before the battle practising for the assault. Facing them was the Bulgarian 9th Pleven Division with 122 guns, in very well prepared defences, commanded by General Vladimir Vazov.