The forces of Don John were mustered at Marche in Luxemburg; those of the states in a plain within a few miles of Namur.

Both armies were nearly equal in number, amounting to nearly twenty thousand each, including a force of two thousand cavalry on each side.

It had been the original intention of the patriots to attack Don John in Namur.

Having learned, however, that he purposed marching forth himself to offer battle, they decided to fall back upon Gemblours, which was nine miles distant from that city.

On the last day of January, they accordingly broke up their camp at Saint Martius, before dawn, and marched towards Gemblours.