On March 17, 1917, the Germans were forced to abandon the whole line of about fifteen miles between the Oise and Andechy, owing to the pressure of French forces. These lines were strongly fortified and had been occupied by the Germans for about two years. The French continued their advance movement on the following day. Their advance guard entered Roye in pursuit of a German contingent that had blown up streets in the interior of the town. About 800 of the civil population which the Germans had not had time to remove received their liberators with a wild enthusiasm that was pathetic to witness. North and northeast of Lassigny the French made further gains, occupying the town and a number of points beyond, and pushing forward past the road between Roye and Noyon. During the night of March 17, 1917, French air squadrons bombarded German organizations in the region of Arnaville, and the factories and blast furnaces at Voelkingen, where a great fire was seen to break out. Stations and roads in the region of Ham and St. Quentin were also bombarded with good results, and all the French aeroplanes returned undamaged. On March 18, 1917, the Germans were in retreat over a front of approximately eighty-five miles from south of Arras on the north to Soissons on the Aisne. They evacuated scores of villages, and the important towns of Peronne, Chaulnes, Nesle, and Noyon. Evidently the Germans had been forced to leave somewhat hurriedly, for many of the places evacuated were only slightly damaged as the result of military operations. British and French troops, keeping in close touch with the German rear guard during the advance, pushed forward to a depth of from ten to twelve miles, and their cavalry entered Nesle about the same time. The occupation of Noyon on the Oise was of special importance, as the nearest point to Paris held by the Germans. The famous Noyon elbow or salient, from which it was expected the Germans would launch an attack on the French capital, now ceased to be a source of anxiety and apprehension to the French fighting forces in this region. Peronne, for which the French had fought desperately for nearly two years, was entered by the British on March 18, 1917, after a brief action with the German rear guard. East of the place the Germans had fired a number of villages as they retreated. Athies, a town of some importance, was reduced to a smoldering ruin and the smoke of its burning buildings could be seen for miles. The Germans displayed their "thoroughness" as they retired by poisoning the wells with arsenic, and setting high-explosive traps into which they hoped the British advance guards would blunder. Bridges over all the waterways were burned and the crossroads carefully mined. [Illustration: The German Retreat on the Western Front, March 18, 1917.]