The retreating army crossed the Semois, a tributary of the Meuse, which it enters below Mezieres, and advanced toward Neufchateau; but they were repulsed by the Germans under the Duke of Wuerttemberg. At Nancy on August 25, 1914, there was another engagement between the garrison of Toul and the army of the Crown Prince of Bavaria; after fierce onslaughts the garrison was compelled to yield and retire. Finally, on August 27, 1914, at Longwy, a fortified town near Verdun, the army of the German crown prince succeeded in bursting into France after a long siege, and marched toward the Argonne. Thus from the western coast almost to Verdun there was a general Franco-British retreat. On August 28, 1914, pressed by the German armies commanded by Von Kluck on the west, by Von Hausen from Dinant and Givet, by Von Buelow from Charleroi and Namur, the Allies were pushed back upon a line stretching roughly from Amiens through Noyon-Le Fere to Mezieres; while their forces east of the Meuse between Mezieres and Verdun were retreating before Duke Albrecht of Wuerttemberg, and to the southeast of Verdun before the Bavarians. All northern France was thus open to the invaders. After the battle of Le Cateau, however, the Germans slackened their pursuit for a very brief interval; partly because the terrific strain of marching and fighting was telling upon them no less than upon the Allies, partly because the engineers had blown up the bridges over every river, canal, and stream, behind the retreating armies, and partly because, under directions from the French commander in chief, General Manoury was organizing a new force on the British left, a new Sixth Army, mainly reserve troops, one corps of line troops, and General Sordet's cavalry. On the right of the British were General Lanrezac's troops; then, between Lanrezac's Fifth Army and the Fourth Army, came a Ninth Army, under General Foch, formed of three corps from the south. Counterattacks were ordered by the French general in chief, continued during the entire retreat and had frequently brilliant results. On August 29, 1914, a corps of the Fifth Army and of the divisions of reserve attacked with success in the direction of St. Quentin with the object of withdrawing the pressure on the British army. Two other corps and a division of reserves joined issue with the Prussian Guard and the Tenth Corps of the German army which debouched from Guise. This was a very violent battle, known under the name of the Battle of Guise. At the end of the day, after various fluctuations in the fight, the Germans were thrown completely over the Oise and the entire British front was relieved. The Prussian Guard on that occasion suffered great losses.