Château-Thierry was occupied by French and American troops on July 21, 1918, the Germans evacuating the place under strong pressure. In their withdrawal from that pivot point on the Marne salient they were closely followed by the Allies' forces, who, cooperating with troops at Vaux and to the northward, swept the Germans back for miles, and beyond the highway to Soissons.
Farther north and almost reaching to Soissons, French and American forces drove on to the Soissons-Château-Thierry highway at Hartennes, and gaining the railway under the Allied guns, threatened Oulchy. As a result of these operations the entire front was straightened out and a gain was made of over seven miles of territory.
On the east side of the salient, between Rheims and the Marne, French and British troops fighting shoulder to shoulder were driving back the Germans, who, opposing a strong resistance, and supported by reserves, were unable to stem the Allies' advance. In the course of the fighting in this sector the French and British occupied the village of Bouilly.
The heavy artillery of the Allies continued on July 21, 1918, to hammer German positions in the districts north of the Marne. Indian scouts who were with Pershing in Mexico were active in gathering information in the river region.
In all sections of the line, from Soissons to Rheims, the hard struggle continued with undiminished intensity. Although the Germans maintained a desperate resistance at the bottom of the Marne salient, it was evident that they would be forced soon to make a wide retreat. This was indicated by the great concentration of German troops at the top of the salient which could only mean that they were making preparations to retire to a new line.
The entire Château-Thierry-Soissons highway from the Ourcq south was now occupied by the Allies. Epieds was captured and territory gained northeast of Mont St. Père, and east of La Croix, and Griselles. Near the last place named the Germans gained some slight temporary advantage, but it had no effect on the continued advance the Allies were making.
Having cleared the Germans out of the district south of the Marne, the Allies were busy constructing bridges and getting troops and supplies across the river. On July 22, 1918, the enemy were trying to keep a hold on the river bank extending from Mont St. Père to east of Reuilly. In the face of a furious fire the French succeeded in getting two strong bodies of troops across the stream at Mézy and Courcelles, who at once started the construction of footbridges while under the grilling fire of the German guns.
The Allies continued to make progress in the Soissons-Rheims salient on July 23, 1918, although the Germans with the support of fresh troops developed stubborn resistance. The most important operation of the day was the advance of the French forces on both sides of the Ourcq southward toward Fère-en-Tardenois, the great German supply center. North of the river General Pétain's troops occupied Montgru on the bank of the stream and two other towns.
South of the Ourcq the Allies were even more successful in gaining ground. Here the French and Americans, cooperating, drove the Germans back nearly a mile beyond the Château-Thierry-Soissons road. Meanwhile, in the Montdidier sector, Foch struck a hard blow at the enemy and achieved a brilliant success. The French troops, attacking on a four-mile front north of Montdidier, made a forward drive of two miles, capturing Mailly-Raineval, Savillers, and Aulvillers. The heights commanding the Avre River were also won, and over 1,500 Germans were captured.
At other points, notably east and northeast of Château-Thierry, at the bottom of the great salient, the French troops, ably assisted by American forces, gained ground. Along almost the entire line between the Ourcq and the Marne German resistance was broken by the resistless onward sweep of the Franco-American forces.