On 30 July, British artillery-fire caused many casualties and the right flank of the 5th Division was hurriedly reinforced by I Battalion, Reserve Infantry Regiment 163 of the 17th Reserve Division, sent from Ytres, which was spotted by British aircrews at Beaulencourt and shelled. During the night II Battalion, Infantry Regiment 23 of the 12th Division was relieved by the I Battalion. On 4 August, a British attack began as the Fusilier Battalion of Grenadier Regiment 12 was being relieved by I Battalion, Infantry Regiment 121 of the 26th Division, which was taking over from the 5th Division, Grenadier Regiment 119 coming into line to the east. A general relief of the German troops on the Somme front was conducted, as the British artillery kept up a steady bombardment of Delville Wood and German observation balloons began to operate between Ginchy and the wood.