1620s Valtellina and Grisons Conflict

Timeline

1. 1620Valtellina valley · LombardyIn July 1620, local Catholic "mobs" in the Valtellina (the Planta family and others) carried out a massacre against Protestant residents, killing hundreds. The Grisons Three Leagues viewed it as a challenge to their sovereign rights, and conflict broke out in full; Spain and the Austrian Habsburgs immediately intervened to support the local Catholic forces.
2. 1621–1622Valtellina and Bregaglia · GraubündenBetween 1621 and 1622, the Grisons Three Leagues organized military operations to recapture the Valtellina, but were met with counterattacks from Spanish troops stationed in Milan and Catholic local armed forces backed by Austria. The two sides repeatedly contested the valley's key routes, and the Grisons failed to restore full control.
3. 1623–1626Alpine passes (Splügen, Saint Gotthard, etc.) · AlpsAfter 1623, France under Richelieu accelerated its southern flank deployments; between 1625 and 1626, French and Grisons allied forces clashed with Spanish-backed armed forces at the Splügen Pass and elsewhere. Austria also intensified its intervention, and the Valtellina conflict thus became embedded in the great-power contest framework of the Thirty Years' War.
4. 1627–1630Valtellina and Milan · ItalyAfter 1627, France, under domestic and military pressures such as the Siege of La Rochelle, could no longer sustain large-scale southern flank operations. Between 1629 and 1630, the parties fell into a diplomatic stalemate over the Valtellina question, and military conflict entered an intermittent phase, but the fundamental issues remained unresolved and the conflict continued until 1639.