The entire 7th Division was reunited on 16 August passed through Brussels on the 20th, and tangled with Smith- Dorrien's II Corps of the BEF near Le Cateau on the 26th. Here, the 66th's sister regiment in the 13th Brigade, the 26th Infantry Regiment (also from Magdeburg), captured 12 field pieces and eight machine-guns. Two days later the division reached Peronne on the Somme, and finally took the town at nightfall on the 28th after several hours of fierce house and street fighting with even the divisional artillery becoming involved. The attack of the 66th and 26th regiments was assisted by the 4th Battery of the 40th Field Artillery Regiment, and a report of one of this battery's officers, Leutnant der Reserve Scheibe, describes the action:
"We entered Peronne with the 1st Bat-talion of the 66th and I was permitted to be the first German artilleryman to ride through the city's gate. From behind the gate jumped a civilian who grabbed my horse's bridle and there, for the only time in the field, I drew my saber and hit him over the head. Occasional shots were being fired from windows and the infantry took cover under the trees along the streets. I remained on my horse. A carbine shot rang out from my battery. I asked the cannoneer who fired it why he had done so. He replied, 'Herr Leutnant, the priest now hanging out of that window across the street was aiming at you.' A little later we lost contact with the infantry and so pulled our guns back. Seeing all the dead Alpine troops (French Alpenjager) and civilians who had taken part in the fight showed us the seriousness of war".Eventually the German drive was stop-ped and following the retreat from the Marne the 7th Division was engaged south of Soissons, and at the end of September was attached to Crown Prince Rupprecht's 6th Army. In early October the division fought in the vicinity of Arras, establishing itself south of the Scarpe River below St. Laurent-Blangy. It held this section until May 1915. However, two months previously the 66th Infantry Regiment was removed from the 7th Division and transferred to the 52nd Division, a new organization.