The Duke of Feria, Fuentes's successor as Governor of Milan, therefore instigated a Catholic insurrection in the Three Leagues, sparking a religious civil war, the Bündner Wirren (Graubünden Disturbances), within the federation. While the Leagues fought among themselves he then invaded the Valtellina in a bid to annex the territory outright and thereby reopen the Spanish Road via Tyrol. This alarmed France, which sent an expeditionary force to the Valtellina under the command of the famed mountain warfare specialist Lesdiguières. The resulting Valtellina War ended in stalemate, and under the Treaty of Monzón (1626) Spain was forced to return the Valtellina to the Three Leagues, but crucially the road through Valtellina to the Stelvio Pass was reopened, enabling troop movements along the Spanish Road to resume.