Outbreak of the Fourth Italian War

Timeline

1. 1521Milan · LombardyAfter the Sforza family was expelled, the Duchy of Milan became the core of contention between Charles V and Francis I. France backed the exiled Sforza faction while the empire consolidated control of Lombardy, and diplomacy between the two broke down.
2. 1521–1522Netherlands · NetherlandsWith the war's outbreak, French forces attacked the Habsburg Netherlands, while imperial troops faced the French and Swiss mercenaries in northern Italy. The conflict quickly expanded from a localized succession dispute into multi-front warfare across Western Europe.
3. 1522–1525Lombardy · LombardyThe two sides repeatedly attacked and defended around Milan; after the Battle of Bicocca the French offensive faltered, but the war continued until the Battle of Pavia brought a resolution. Lombardy became the main theater of the Fourth Italian War.