Surrender of Julich (1634). Oil on canvas. 307 x 381. The Siege of Jülich was a siege that took place between 5 September 1621 and 3 February 1622, during the Palatinate campaign of the Thirty Years' War. After five months of siege the Spanish army under Ambrosio Spinola took the Dutch-occupied fortress of Jülich, compelling its garrison to surrender. The defenders, some 2,000 men, surrendered on 3 February, after five months of siege. Cardinal de la Cueva in Brussels had reported to the king that han sentido mucho los olandeses la pérdida de Juliers. In line with her instructions to appoint Spaniards rather than Spanish Netherlanders as military governors of towns conquered from the Dutch, the Archduchess Isabella named Don Diego de Salcedo, reportedly a persona de muy buenas partes as governor of Jülich.