of communication On the night of Allied forces north of the Somme were cut off by the German advance to St Omer and Boulogne, which isolated the BEF from its supply in Brittany, at Cherbourg in Normandy and at Nantes. Dieppe was the main medical base of the BEF and Le Havre the principal supply and ordnance source. From St Saëns to Buchy, north-east of Rouen, lay the BEF ammunition depot; infantry, machine-gun and base depots were at Rouen, Évreux and l'Épinay. A main railway line linking the bases and connecting them with bases further west in Normandy and with the BEF in the north, ran through Rouen, Abbeville and Amiens. Brigadier Beauman was responsible for base security and guarding under construction by troops drawn from the Royal Engineers, Royal Army Ordnance Corps, Royal Corps of Signals and older garrison troops. Further south, in the Southern District, were three Territorial divisions and the 4th Border Regiment, 4th Buffs and the 1st/5th Sherwood Foresters, lines-of-communication battalions, which were moved into the Northern District on 17 May as a precaution. Rail movements between the bases and the Somme quickly became difficult, due to congestion and German bombing, the trains from the north mainly carrying Belgian and French troops and the roads filling with retreating troops and refugees. Beauman lost contact with GHQ and was unable to discover if Allied troops were going to dig in on the Somme or further south. On 18 May, Major-General Philip de Fonblanque, commanding the lines-of-communication troops, ordered Beauman to prepare defences in the Northern District. Beauforce was improvised from the 2nd/6th East Surrey of the 12th (Eastern) Infantry Division, 4th Buffs, four machine-gun platoons and the 212th Army Troops Company RE. Vicforce (Colonel C. E. Vickary) took over five provisional battalions, created from reinforcement troops in BEF infantry and general base depots, which held plenty of men but few arms and little equipment. Beauforce was sent by road to Boulogne on 20 May but the Germans had already cut off the port and it returned to the 12th Division near Abbeville. When German troops captured Amiens on 20 May and then began patrolling south of the river, their appearance caused panic and alarmist reports, in the absence of reliable information. Beauman ordered the digging of a defence line along the Andelle and Béthune rivers, which were the most effective tank obstacles south of the Bresle river,