The French have lost Alessandria, …

…Pavia, and …

…Como by January 1522; and …

…Francesco II Sforza, bringing further German reinforcements, has slipped past a Venetian force at Bergamo to join Colonna in Milan.

Francesco II is the second son of Ludovico Sforza and Beatrice d'Este.

When Ludovico was ousted from Milan in the course of the Italian Wars, he had brought Francesco with him to the court of the Emperor Maximilian I, who had married a Sforza, Francesco's cousin Bianca Maria.

Francesco had been assigned to an ecclesiastical career.

His father had been imprisoned in Loches by Louis XII of France, and died in 1508, but when Charles V re-conquered Milan from the French in 1521, Francesco had been appointed its duke, the last of the family to hold this title.

His sovereignty, however, remains circumscribed by the military occupation of Milan by Spanish troops.

Lautrec has meanwhile been reinforced by the arrival of sixteen thousand fresh Swiss pikemen and some further Venetian forces, as well as additional companies of French troops under the command of Thomas de Foix-Lescun and Pedro Navarro; he had also secured the services of the condottiere Giovanni de' Medici, who brings his Black Bands into the French service.

Composed primarily of arquebusiers—including Europe's first mounted arquebusiers—the company is considered to be the finest Italian troops available.

Initially in the service of Charles de Lannoy and the Pope, their name comes from their black mourning colors for the death of Pope Leo X.

The French proceed to attack Novara and …

…Pavia, hoping to draw Colonna into a decisive battle.

Colonna, leaving Milan, fortifies himself in the monastery of Certosa south of the city.

Considering this position to be too strong to be easily assaulted, …

…Lautrec attempts instead to threaten Colonna's lines of communication by sweeping around Milan to Monza, cutting the roads from the city into the Alps.

Lautrec is suddenly confronted, however, with the intransigence of the Swiss, who form the largest contingent of the French army.

They complain that they have not received any of the pay promised them since their arrival in Lombardy.

The Swiss captains, led by Albert von Stein, demand that Lautrec attack the Imperial army immediately—else the mercenaries will abandon the French and return to their cantons.

Lautrec reluctantly acquiesces and marches south towards Milan.

Colonna has meanwhile relocated to a formidable new position: the manor park of Bicocca, about four miles (six kilometers) north of Milan.

The park is situated between a large expanse of marshy ground to the west and the main road into Milan to the east; along this road runs a deep wet ditch, which is crossed by a narrow stone bridge some distance south of the park.

The north side of the park is bordered by a sunken road; Colonna deepens this and constructs an earthen rampart on the southern bank.

The Imperial artillery, placed on several platforms jutting forward from the earthworks, is able to sweep the fields north of the park as well as parts of the sunken road itself.

The entire length of the north side of the park is less than six hundred yards (five hundred and fifty meters), which permits Colonna to place his troops quite densely.

Immediately behind the rampart are four ranks of Spanish arquebusiers, commanded by Fernando d'Avalos, Marquess of Pescara; they are backed by Spanish pikemen and German landsknechts under Georg Frundsberg.

Most of the Imperial cavalry is placed at the south end of the park, far behind the infantry; a separate force of cavalry is positioned to the south, guarding the bridge.