Charles V.cared more for the coasts of the Mediterranean than for those of the Channel; he flattered himself that he would make of Marseilles a southern Calais, which should connect Germany with Spain, and secure their communications, political and commercial.
Bourbon objected and resisted; it was the abandonment of his general plan for this war and a painful proof how powerless he was against the wishes of the two sovereigns, of whom he was only the tool, although they called him their ally.

Being forced to yield, he began the siege of Marseilles on the 19th of August.

The place, though but slightly fortified and ill supplied, made an energetic resistance; the name and the presence of Bourbon at the head of the besiegers excited patriotism; the burgesses turned soldiers; the cannon of the besiegers laid open their walls, but they threw up a second line, an earthen rampart, called the ladies' rampart, because all the women in the city had worked at it.

The siege was protracted; the re-enforcements expected by Bourbon did not arrive; a shot from Marseilles penetrated into Pescara's tent, and killed his almoner and two of his gentlemen.

Bourbon rushed up.