outside+pressures+that+could+lead+to+collapse

__ Outside pressures that could lead to collapse __

While Spinola and the Spanish army were focused on the Netherlands, the war seemed to go in Spain's favor. But 1627 saw the collapse of the Castilian economy. The Habsburgs had been debasing their currency to pay for the war and prices exploded, just as they had in previous years in Austria. Until 1631, parts of Castile operated on a barter economy owing to the currency crisis, and the government was unable to collect any meaningful taxes from the peasantry and had to depend on revenue from its colonies. The Spanish armies, like others in German territories, resorted to "paying themselves" on the land. Olivares had backed certain taxation reforms in Spain pending the end of the war, but was blamed for another embarrassing and fruitless war in Italy. The Dutch, who during the Twelve Years' Truce had made increasing their navy a priority, (which showed its maturing potency at the Battle of Gibraltar 1607), managed to strike a great blow against Spanish maritime trade with the capture of the treasure fleet by captain Piet Hein, on which Spain had become dependent after the economic collapse

( information from wikipedia)