10th-11th May 1940 - Belgium
The new front to which the French and British armies were moving ran from Sedan in the south to Antwerp in the north. Except in one twenty-mile sector it was covered by watercourses which served as tank obstacles. From Sedan the front followed the Meuse through Givet and Dinant to the fortress of Namur. From there to the River Dyle at Wavre was the one unprotected sector, known as the Gembloux gap. The front was then covered by the Dyle from Wave to Louvain, running behind canalised rivers to Antwerp and the sea.
The Belgians had claimed to have put fortifications in place in the Gembloux gap, but unfortunately this turned out not to be the case.
The French High Command expected the main German attack in the Belgian plain between Namur and Antwerp, so they had concentrated strong forces there. On the right the French First Army behind the Gembloux gap held a front of approximately twenty-five miles with eight infantry divisions and two light armoured divisions of the Cavalry Corps operating out in front in order to buy time for the other divisions to close up and dig in.
In the centre, the British force would be expected to hold seventeen miles of the Dyle, from Wavre to Louvain, had nine divisions deployed in depth with three in the initial front line. On the British left the Belgian Army was falling back to continue the Allied line of defence to the sea. The French Seventh Army advancing to Antwerp had three infantry divisions. The reserve, the other six divisions of 7th Army, was moving up to the area around Cambrai.
In the sector farther south between Longwy, Sedan and Namur, where the Ardennes and the River Meuse were thought by the French Command to make an armoured attack impracticable, the defence was much weaker. The Ninth and Second Armies were mad up chiefly of Series A and Series B divisions. Reinforcements from units of general reserve were on a smaller scale and those units were equipped with less modern equipment.
The Second Army holding about forty miles of the front had five infantry divisions between Longwy and Sedan with two cavalry divisions and a cavalry brigade in front; the Ninth Army held a front of over fifty miles with seven infantry divisions, two light cavalry divisions composed largely of horsed units with a few light tanks, and a brigade of Spahis out in front.
The reserves held behind the armies, while strong in the north, were much weaker to the south. The general reserve which General Georges had at his disposal was weak, namely thirteen divisions. It was much spread out and unable to act quickly in a counter-stroke. This was partly because the main armoured attack was expected to come through the Belgian plain, and so it would be necessary to slow this to allow these reserves, and the main French armour, time to group for a counterattack. This assumed that the German advance would be slow enough to allow for this.
The French High Command had made another miscalculation which affected the defensive line. It was assumed that the Belgians' defence of their frontier and the delaying action of the French and British cavalry screen would be enough to prevent the German forces from reaching the main line of resistance in the north - the Dyle line - before the Allies' move forward was completed. This assumption proved to be at fault so far as the French Ninth Army was concerned.
The Belgian plan was to fight a delaying action on the Albert Canal from Antwerp to the Meuse and thence along the Meuse from Liége to Namur, untill the Allied forces could reach the Dyle. The Belgian Army was then to withdraw to the left sector of that line, between Louvain and the sea. But early on the opening morning of the campaign, before the German forces reached Maastricht, the Belgian defence of the Albert Canal front had been gravely prejudiced by the loss of the bridges at Briedgen, Veldwezelt and Vroenhoven, immediately west of Maastricht, and of the nearby frontier fortress of Eben Emael which was designed to protect them.
The Cavalry Corps was positioned in front of the main body of French 1st Army as a covering force. It was known that the infantry would need time to dig in along the defensive line, but General Prioux was shocked to discover that the field and permanent fortifications the Belbians claimed were covering the Gembloux gap were virtually non-existent. The only way to buy more time was for the Cavalry Corps to move further forward then fight a delaying action to gain the required time.
The Cavalry was in place on May 11th. On the left, the 3e DLM was in touch in the north with British and Belgian cavalry in the Tirlemont area. The Hotchkiss H-35 light tanks were at the front, the medium S-35's being the reserve positioned behind them. South of Crehen the 2nd DLM was positioned, covered along almost the whole of its front by the Mehaigne creek, down to Huy on the Meuse river. The biggest worry was the southern part of 3e DLM, opposite the dangerously open terrain facing Hannut. With the infantry divisions still not yet at their defence line, there was no general reserve to back up the Cavalry Corps. If a disaster happened, there would be nothing to stop German armour breaking through the Gembloux gap and getting behind the Allies defensive line. To cover this, General Geroud released the British 1st Armoured Brigade to move to the east of Mons. It was hoped that this was just a precaution - he did not wish to break up his reserve into small units - but some sort of cover was needed, and if the Cavalry Corps held as hoped, 1st Armoured Brigade would rejoin the rest of 7th Army.