Levies of Walloons and Germans were made without delay by order of Archduke Albert and under guidance of Spinola, so that by midsummer the army was swollen to 18,000 foot and 3000 horse.
With these the great Genoese captain took the field in the middle of August.

On the 22nd of that month the army was encamped on some plains mid-way between Maestricht and Aachen.

There was profound mystery both at Brussels and at the Hague as to the objective point of these military movements.

Anticipating an attack upon Julich, the States had meantime strengthened the garrison of that important place with 3000 infantry and a regiment of horse.

It seemed scarcely probable therefore that Spinola would venture a foolhardy blow at a citadel so well fortified and defended.