On 26 August, German forces captured Valenciennes and began 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 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 (1914) (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.