Two combat companies of the battalion made way to the front on December 13 in the sector of the Marquises. Starting from October 1914, the battalions relayed each other and were either in line within trenches sector of Prunay and the city of des Marquises or being prepositioned in the villages of Verzenay, Mailly and along the Canal de l'Aisne à la Marne. The regiment was permanently exposed to the duel of artillery fire barrages and subjected to close quarters combat. The 2nd Marching Regiment of the 1st Foreign Regiment was extracted from allocated positionings between April 22 and 24 of 1915. The regiment garrisoned from April 24 to 25 in Villers-Allerand, Louvois, Montchenot and Sermiers until being train transported to Aubigny-en-Artois. On the 27th, the regiment was at Villers-Brûlin and at Béthonsart. Already since the 28th, the regiment was posted at the front and relieved elements of the 77th French Infantry Division (). Front line commands of the division were accordingly stationed. On May 9, 1915, at 1000, following a small preparation of artillery, the regiment's battalions launched the assaults successively. The combat engagement for the regiment counted 75 officers and 3,822 men. In 90 minutes of combat, the regiment managed to gain all set objectives (Ouvrages Blancs - ouvrage de Nuremberg) and attained finally the route de Béthune then cote 140. Due to a lack of reinforcement, the regiment was only capable of holding for two hours on the last objective and was forced to unfold on cote 123 which was held till the following morning. The losses for the regiment during the confrontation were considerable: 1889 men, near half of effectifs were placed out of combat ( killed or disappeared: 20 Officers and 933 men - wounded: 28 Officers and 956 men ). The tribute of Officers was eloquent: the regimental commander, colonel Cot was wounded, while the regiment's 3 battalion commanders were killed ( Commandant Noiré, Commandant Muller and Commandant Gaubert ). Also, the loss of the previous regimental commander, Colonel Pein, was recently deplored while leading the 1st Brigade of the Moroccan Division (). On May 30, the regiment was partially reconstituted and recounted 4 new battalions due to the arrival reinforcements. On June 4 and 5, 325 Italians left the regiment to rejoin their Armed Forces in their country which recently entered the war.