from the junction with the Third Army south of Montmédy, westwards to Sedan, Mezières and Fumay, facing the 4th Army and the Fifth Army was between Fumay and Maubeuge, with the 3rd Army advancing up the Meuse valley from Dinant and Givet into a gap between the Fourth and Fifth Armies and the 2nd Army pressed forward into the angle between the Meuse and Sambre directly against the Fifth Army. On the far west flank of the French, the BEF prolonged the line from Maubeuge to Valenciennes against the 1st Army and Army Detachment von Beseler masked the Belgian Army at Antwerp. On 26 August, German forces captured Valenciennes and conducted the Siege of Maubeuge Leuven (Louvain) was sacked by German troops and the Battle of Le Cateau was fought by the BEF and the 1st Army. Longwy was surrendered by its garrison and next day, British Royal Marines and a party of the Royal Naval Air Service (RNAS) landed at Ostend; Lille and Mezières were occupied by German troops. Arras was occupied on 27 August and a French counter-offensive began at the Battle of St. Quentin (also known as the Battle of Guise On 29 August the Fifth Army counter-attacked the 2nd Army south of the Oise, from Vervins to Mont Dorigny and west of the river from Mont Dorigny to Moy towards St. Quentin on the Somme, while the British held the line of the Oise west of La Fère. Laon, La Fère and Roye were captured by German troops on 30 August and Amiens the next day. On 1 September Craonne and Soissons were captured and on 5 September the BEF ended its retreat from Mons, German troops reached Claye, from Paris, Reims was captured, German forces withdrew from Lille and the First Battle of the Marne (Battle of the Ourcq) began, marking the end of the Great Retreat of the western flank of the Franco-British armies. By 4 September the First and Second Armies had slowed the advance of the 7th and 6th armies west of St. Dié and east of Nancy, from where the Second Army had withdrawn its left flank, to face north between Nancy and Toul. A gap between the left of the Second Army and the right of the Third Army at Verdun, which faced north-west, on a line towards Revigny against the 5th Army advance, west of the Meuse between Varennes