In northern France, German troops engaged in mutual outflanking attempts, from the Aisne northwards since September, had reached Arras. Lens was captured by I Bavarian Reserve Corps on 5 October. Three German cavalry corps had attempted another flanking manoeuvre to the north and IV Cavalry Corps had reached Zwartberg and Mont des Cats near Ypres. The advance of the German army threatened to block the western retreat route of the Belgian army out of Antwerp. On 6 October discussions between the British and Belgians, led to a decision to withdraw the field army to the west bank of the Scheldt, where it could maintain contact with a relieving force and avoid the danger of being trapped on the east bank. On the night of the 1st, 3rd and 5th divisions crossed the river and joined the Cavalry, 4th and 6th divisions, as the eight forts of the inner ring were taken over by fortress troops. Intervening trenches between were occupied by the two British naval brigades and the 4th and 7th Fortress regiments, with the Belgian 2nd Division and British Marine Brigade in reserve. The British forces under the command of Major-General Archibald Paris, were ordered by First Lord of the Admiralty, Winston Churchill, to continue the defence for as long as possible and to be ready to cross to the west bank rather than participate in a surrender.