A German raid on an outpost of the 51st Battalion in the 13th Brigade resulted in five men being taken prisoner in an area previously held be the French, thus raising concerns amongst the senior commanders that the Germans might become suspicious or extract information from the prisoners and so go on a state of heightened alert. Captured German reports later showed that despite intensive questioning the Australian prisoners did not divulge anything beyond their name and unit, and it went further by praising these men and holding them as a model on how their own soldiers should react. As a result of the raid it was decided that the Canadians could not relieve the 13th Brigade until the very last minute, therefore depriving General Maclagan of one of his brigades, so Monash took the decision to temporarily transfer one of the AIF 1st Division brigades which was due to arrive in the coming days. Later that night the 1st Brigade having been hastily despatched, arrived for their involvement in the forthcoming operation. To the north of the river Somme a German counter-attack retook the ground taken a week previously by the 8th Brigade and now held by Butler’s III Corps, taking 8 officers and 274 other ranks prisoner. There was no sign that the Germans discovered anything new, but for Monash this vulnerability of his left flank across the river was evident and causing great concern.