Then Foch, the great French strategist and Allied generalissimo, struck the blow for which he had patiently bided his time! Apparently having advance information of the German plans, or perhaps surmising them, General Foch had been preparing a surprise for the Crown Prince. In the forest of Villers-Cotterets on the German right flank, he had quietly massed large forces, including some of the best French regiments, together with the foreign legion, Moroccan and other crack troops, and many Americans. Everything possible had been done to keep these troop movements secret from the enemy. On Thursday morning, July 18, 1918, a heavy attack was launched in force at the Germans under General von Boehm all along the line from Chateau Thierry on the Marne to the Aisne river northwest of Soissons. The Germans were taken completely by surprise, and town after town was captured from them with comparatively slight resistance. When the first shock of surprise was over, their resistance stiffened, but the Allies continued to advance. Mounted cavalry were once more used to assist the infantry in the open, while tanks in large numbers were used to clear out enemy machine-gun nests. The American troops, fighting side by side with the French, did their work in a manner to excite the admiration of their allies, and acquitted themselves like veterans. Thousands of prisoners were taken, with large numbers of heavy guns and great stores of ammunition, besides thousands of machine guns, many of which were turned against the enemy. The strategy of General Foch received world-wide applause. His master stroke met with immediate success. By the 20th of July Soissons was threatened by the Allies. The Germans, finding themselves caught in a dangerous salient and attacked fiercely on both flanks, hurriedly retreated to the north bank of the Marne and were rapidly pressed back farther. Their condition was critical and the German Crown Prince was obliged to call for assistance from Crown Prince Rupprecht of Bavaria, commanding in the north. Taking advantage of this, the British and French in the north made frequent attacks, gaining ground and taking prisoners at numerous points. For ten days the Allies continued their victorious progress on both sides of the Soissons-Reims salient, the Germans continuing to retire under strong pressure. They were forced back to the Oureq river, then to the Vesle, where they made a determined stand. Fère-en-Tardenois and Fismes fell into the hands of the victorious French and Americans, the latter gaining a notable victory in the occupation of Fismes over the vaunted Prussian guards, who had been brought up to endeavor to stay their progress. The first week of August saw most of the Reims salient wiped out by the German retreat, while rear-guard actions were being fought along the Vesle as the Germans sought defensive positions farther in the rear.