Camino Español
Much of the fighting focused on different parts of the Spanish Road, an overland supply route connecting Spanish possessions in Northern Italy to Flanders. After 1601, it was rarely used for moving soldiers, but remained vital for trade, and went through areas essential to French security. At the start of 1635, France threatened the Road at a variety of points; as well as 27,000 men under Urbain de Maillé-Brézé in Picardy, they had armies in Champagne, Lorraine, the Sarre, and the Valtellina.