A victory had already been gained in Luxembourg, close to the little town of Avein, over Prince Thomas of Savoy, the duke-regnant's brother, who was embroiled with him, and whom Spain had just taken into her service.

The campaign of 1635 appeared to be commencing under happy auspices.

These hopes were deceived; the Low Countries did not respond to the summons of the king and of his confederates; there was no rising anywhere against the Spanish yoke; traditional jealousy of the heretics of Holland prevented the Flanders from declaring for France; it was necessary to undertake a conquest instead of fomenting an insurrection.

The Prince of Orange was advancing slowly into Germany; the Elector of Saxony had treated with the emperor, and several towns were accepting the peace concluded between them at Prague; Bernard of Saxe-Weimar, supported by Cardinal Valette, at the head of French troops, had been forced to fall back to Metz in order to protect Lothringen and Elsass.

In order to attach this great general to himself forever, the king had just ceded to Duke Bernard the landgravate of Elsass, hereditary possession, as it was, of the house of Austria.
The Prince of Conde was attacking Franche-Comte; the siege of Dole was dragging its slow length along, when the emperor's most celebrated lieutenants, John van Weert and Piccolomini, who had formed a junction in Belgium, all at once rallied the troops of Prince Thomas, and, advancing rapidly towards Picardy, invaded French soil at the commencement of July, 1636.