An especially interesting example, given that the Swiss Confederation usually did all they could to prevent Swiss-on-Swiss fighting.

Apparently in this case, a treaty had already been signed and the bulk of the Swiss defenders had returned home prior to the battle, intending to cede Milan to the French. The Swiss who stayed to fight were a smaller force of fresh reinforcements who were hungry for plunder and misinformed about the strength of the French army. They actually launched a surprise attack against the French instead of waiting for the French to reach Milan.