As agreed at Compiègne in 1635, the French replaced Swedish garrisons in Alsace; prior to his death in 1639, Bernard of Saxe-Weimar won a series of victories over the Imperials in the Rhineland, notably the capture of Breisach in December 1638. By severing the Spanish Road, it forced Spain to reinforce their armies in Flanders by sea, which was dominated by the Dutch navy; in 1639, they destroyed a large supply convoy at the Downs. They also attacked Portuguese possessions in Africa and the Americas, then part of the Spanish Empire; Madrid's inability to prevent this caused increasing unrest in Portugal.