The 30th Armoured Brigade commanded by Brigadier Nigel Duncan and was equipped with crab flails. Its three regiments were the 22nd Dragoons, the 1st Lothian and Border Horse and the 2nd County of London Yeomanry (Westminster Dragoons). Each of the brigade's Crab regiments was subdivided in a headquarters and three squadrons each of which had three troops of five Crabs. When engaged in line clearing three crabs of a troop advanced in formation over a 24 foot (7.30m) wide front, while the other two tanks remained in reserve to provide covering fire for the three actually mine-clearing. To enable the drivers of the Crabs to maintain formation, posts with lamps on them were fitted to the rear of the tanks. When not in use the posts could be unshipped and stowed in a special locker. The 1st Assault Brigade RE was under the orders of Brigadier G.L. Watkinson was equipped with AVRE's and also fielded three regiments - the 5th, 6th and 42nd Assault Regiments. RE. The 1st Tank Brigade was composed of the 11th Royal Tanks Regt., the 42nd RTR (23rd London Regt.) and the 49th RTR. The brigade was equipped with CDL's. However, Gen. Hobart's division was not engaged as a single bloc with its specialist material, but was spread out among the three assault divisions. Thus the 3rd.Division on Sword Beach was supported by the Crabs of A Squadron of the 22nd Dragoons and the AVRE's of the 77th and 79th Squadrons of the 5th Assault Regt RE. The 3rd Canadian Division on Juno Beach had the support of the Crabs of B Squadron of the 22nd Dragoons and the AVRE's of the 25th and 80th Squadrons of the 5th Assault Regt. RE. The 50th Northumberland Div. was supported on Gold Beach by the Crabs of Band C Squadrons of the Westminster Dragoons and the AVRE's of the 81st and 82nd Squadrons of the 6th Assault Regt. RE. The special armour was to precede the assault waves of the infantry coming ashore to dispose of the obstacles placed by the Germans enjoying the element of surprise over the defenders. These were some of the tasks assigned to them: Crossing anti-tank walls and ditches by placing SBG's or breaching them with the flying dustbin bombs. The latter were also responsible for dealing with the defenders' guns and bunkers. Charges were placed by hand by AVRE crews who dismounted. Ditches and bomb craters were filled with fascines and bridged over by SBG's. Steel beach obstacles were knocked over by the flying dustbins, gunfire from the Crabs or pushed aside by the bulldozers. The Crabs exploded the mines or the Bullhorn ploughs dug them up. The AVRE's fitted with bobbins unrolled their flexible carpets over the patches of soft clay. Once on shore the DD's were used as conventional tanks. The amphibious tanks was a part of the specialist vehicles trained by the 79th Armoured Div., but for D-Day they did not belong to the division.