Valtellina (vältāl-lē´nä), Alpine valley of the upper Adda River, c.75 mi (120 km) long, in Lombardy, N Italy, extending from Lake Como to the Stelvio Pass. The main towns are Sondrio and Tirano. The valley is a fertile agricultural region, known for its wine. With the adjoining counties of Bormio and Chiavenna, the Valtellina was seized (1512) from Milan by the Grisons, which subsequently ruled the district—its richest and most populous possession—as a subject territory. By the start of the Thirty Years War (1618–48), the stoutly Roman Catholic inhabitants of the Valtellina were ready for revolt against the Grisons, the majority of whose population was Protestant; in 1620 they rose and massacred their Protestant masters. These internal troubles quickly assumed European proportions, because the valley commanded the passages between Austria and the Grisons and Venice and Spanish-held Milan. The Valtellina became the pawn of the participants in the Thirty Years War and the victim of their complicated intrigues. The massacre of 1620 led to a series of military interventions by Spain, Austria, the pope, the Catholic party of the Grisons, France, and the Protestant majority of the Grisons (largely financed by Venice). The valley was sacked in turn by these armies and in 1627 passed under Spanish control; transportation of Spanish reinforcements through the Valtellina into Germany contributed to several victories by the imperial party, notably at Nördlingen (1634). When France fully entered the war on the Protestant side, a French army was again dispatched (1635) to the Valtellina. Henri de Rohan conquered the valley but failed to restore it to the full control of his Grisons allies. Incensed, the Grisons Protestants, led by the preacher-soldier George Jenatsch, secretly negotiated with the Catholic powers, who promised to restore the Valtellina to the Grisons if the French were expelled. However, Rohan, ill and weakly supported by the French government, had to evacuate the Grisons in 1637. By the Peace of Milan (1639) the Grisons fully recovered the Valtellina; it remained in the Grisons until 1797, when it was incorporated into the Cisalpine Republic. The Valtellina passed (1815) to the Lombardo-Venetian kingdom (held by Austria), and later it passed (1859) to Italy.