to protect Dieppe and Rouen from the east. Bridges were prepared for demolition and obstacles placed on their approaches. Prelude German preparations On 21 May, prepared the Somme bridges for demolition and outposts were pushed as far south as Moyenneville, Huppy, Caumont and Bailleul, where anti-tank guns had been dug in and camouflaged among the woods. Later in the day orders arrived for the advance to resume northwards towards the Channel Ports but parts of the group were held back in reserve on 22 May, due to the Allied counter-attack at Arras on 21 May, until reinforced by the XIV Corps and the 2nd Motorised Division, which began to take over the defence of the Somme bridgeheads the next day. The staff of Engineer Regiment 511 (Colonel Müller) and Engineer battalions 41 and 466 were added to the 2nd Motorised Division, ready to blow the Somme bridges in an emergency as the division probed south to the Bresle, Aumale and Conty. When the XIV Corps arrived it was to continue to expand the bridgeheads on the south bank. Allied preparations After a reform of the French command structure in January 1940, the Allied chain of command in the region around Abbeville was Maxime Weygand (Supreme Commander from 19 May), General Alphonse Joseph Georges (Commander North-Eastern Front [including the BEF]), General Besson (), General Aubert Frère (Seventh Army) General Robert Altmayer (Group A/Tenth Army) and General Marcel Ihler (IX Corps), in command of Evans and Fortune, with the BEF (Field Marshal Lord Gort) with a veto over French orders by appeal to the War Office (Secretary of State for War Oliver Stanley) and having vaguer responsibilities for the British forces south of the Somme. In the afternoon of 18 May, Georges ordered the Sixth Army, Seventh Army and the (4e DCr, Colonel Charles de Gaulle) to organise the defence of the Crozat Canal line and the Somme, between Ham and Amiens. The Seventh Army was ordered to keep its forces ready for a counter-attack at the left flank of the attacking German forces. Troops withdrawing from Belgium were to organise a defence line further west, around Abbeville to the English Channel. From 19 May to 4 June the SNCF railways moved divisions to the area from the Aisne to the Somme, despite German air superiority and the bombing of railway lines and junctions. The 2nd Armoured Brigade (Brigadier F. Thornton) consisted