Souham, who commanded in the temporary absence of Pichegru, had formed his own plan. Finding himself with the major part of his forces between York and Clerfayt, he had decided to impose upon the former by means of a covering detachment, and to fall upon Clerfayt near Rousselaer with the bulk of his forces. This plan, based as it was on a sound calculation of time, space, strength and endurance, merits close consideration, for it contains more than a trace of the essential principles of modern strategy, yet with one vital difference, that whereas, in the present case, the factor of the enemy's independent will wrecked the scheme, Napoleon would have guaranteed to himself, before and during its development, the power of executing it in spite of the enemy. The appearance of fresh allied troops (Kinsky) on his right front at once modified these general arrangements. Divining Coburg's intentions from the arrival of the enemy near Pont-a-Marque and at Lannoy, he ordered Bonnaud (Lille group, 27,000) to leave enough troops on the upper Marque to amuse the enemy's leftmost columns, and with every man he had left beyond this absolute minimum to attack the left flank of the columns moving towards Tourcoing, which his weak centre (12,000 men at Tourcoing, Mouscron and Roubaix) was to stop by frontal defence. No role was as yet assigned to the principal mass (50,000 under Moreau) about Courtrai. Vandamme's brigade was to extend along the Lys from Menin to Werwick and beyond, to deny as long as possible the passage to Clerfayt. This second plan failed like the first, because the enemy's counter-will was not controlled. All along the line Coburg's advance compelled the French to fight as they were without any redistribution. But the French were sufficiently elastic to adapt themselves readily to unforeseen conditions, and on Coburg's side too the unexpected happened. When Clerfayt appeared on the Lys above Menin, he found Werwick held. This was an accident, for the battalion there was on its way to Menin, and Vandamme, who had not yet received his new orders, was still far away. But the battalion fought boldly, Clerfayt sent for his pontoons, and ere they arrived Vandamme's leading troops managed to come up on the other side. Thus it was not till 1 A.M. on the 18th that the first Austrian battalions passed the Lys.