noon
As soon as day broke Tilly became aware of what was being done , and two batteries opened fire upon the work at the head of the bridge and against the bridge itself ; but the low and swampy nature of the ground on the Imperialist side of the river prevented his placing the batteries in a position from which they could command the works , and their fire proved ineffective in preventing the construction of the bridge . Seeing this , Tilly at once commenced preparations for arresting the further advance of the Swedes . To reach his position they would be obliged to cross the swampy ground exposed to the fire of his troops , and to render their progress still more difficult he proceeded to cut down large trees , lopping and sharpening their branches to form a chevaux-de-frise before his troops . All the morning a heavy cannonade was kept up on both sides , but by noon the bridge was completed and the advance guard of the Swedes , led by Colonels Wrandel and Gassion , advanced across it . As the other brigades were following , Tilly directed General Altringer to lead his cavalry against them . Altringer led his troops round the end of the marsh and charged with great bravery down upon the Swedes . These , however , had time to form up , and a tremendous fire of musketry was poured into the Imperialist horse , while the round shot from the three Swedish batteries ploughed their ranks in front and on both flanks .