Then Ludovico made the mistake of stopping to besiege the castle instead of marching on to Mortara with the new reinforcement.

The result of this was that Louis XII, to whom runners had been sent by Trivulce, understanding his perilous position, hastened the departure of the French gendarmerie who were already collected to cross into Italy, sent off the bailiff of Dijon to levy new Swiss forces, and ordered Cardinal Amboise, his prime minister, to cross the Alps and take up a position at Asti, to hurry on the work of collecting the troops.

There the cardinal found a nest-egg of 3000 men.
La Trimouille added 1500 lances and 6000 French infantry; finally, the bailiff of Dijon arrived with 10,000 Swiss; so that, counting the troops which Trivulce had at Mortara, Louis XII found himself master on the other side of the Alps of the first army any French king had ever led out to battle.

Soon, by good marching, and before Ludovico knew the strength or even the existence of this army, it took up a position between Novarra and Milan, cutting off all communication between the duke and his capital.

He was therefore compelled, in spite of his inferior numbers, to prepare for a pitched battle.
But it so happened that just when the preparations for a decisive engagement were being made on both sides, the Swiss Diet, learning that the sons of Helvetia were on the paint of cutting one another's throats, sent orders to all the Swiss serving in either army to break their engagements and return to the fatherland.