The Matilda Mk I, (A11) and Matilda II (A12) infantry tanks fought together in France as part of the 1st Army Tank Brigade of the British Expeditionary Force in the Battle of France. They participated in the defence and counter-attack operation at Arras against the invasion by Nazi Germany in May 1940, temporarily discomfiting the 7th Panzer Division under Rommel. In the battle, elements of motorized SS regiment "Totenkopf" (later to be expanded into SS-Division "Totenkopf")—were overrun, their standard &lt;a href="3.7%20cm%20PaK%2036"&gt;PaK 36/37&lt;/a&gt; anti-tank guns proving ineffective against the heavily armoured British Matilda tank. Rommel committed some of his armour to local counterattacks, only to find the guns of the "Panzer" II and Panzer 38(t) tanks could not penetrate the Matildas' armour. Desperate to prevent a British breakthrough, Rommel ordered the division's FlaK 18 anti-aircraft guns and field guns be formed into a defensive line and fire anti-tank and HE rounds in a last-ditch effort to stop the Matildas, and this stopped the British tanks. The attack made the German commanders nervous, and the battle is historically credited with shaking the confidence of the German High Command (OKW) and it may have been one of the factors for the surprise German halt on 24 May that gave the BEF the slimmest of opportunities to begin evacuation from Dunkirk. The main British force consisted of only 58 machine gun armed Matilda Is and 16 QF 2-pounder gun armed Matilda IIs supported by a few lighter armoured vehicles.