If in most matters of government the kingdom was left to its own devices, in the realm of defence it was required to play a more active role in support of the Monarchy. The policy of the Union of Arms, elaborated under the Count Duke of Olivares in the 1620s, aimed to spread Spain's military burden a little more evenly instead of allowing it to fall mainly on an exhausted Castile. The scheme came spectacularly to grief, of course, in Catalonia, where it provoked the great revolt of 1640. And that fatal decade saw revolts throughout the peripheral provinces – Portugal, Naples, Sicily, even Aragon if we count the abortive conspiracy of the Duke of Híjar. Standing like a rock in the tempest was Valencia.

In the Cortes of 1626 the kingdom agreed to give 1,080,000 lliures for the Union of Arms. In 1630 and until 1642 ‘voluntary’ levies raised and equipped by senyors and towns in reply to requests from the Crown became a new and regular feature of the Valencian scene. Combined with ordinary recruiting on the open market by commissioned officers, these campaigns may have drained 12,000 or 14,000 young adult males from the kingdom by 1637. From 1637, in fact, the policy took a new turn, when a form of general conscription was introduced – one man was taken from every 100 households to serve a summer campaign against the French, who were then intensifying their pressure along the Pyrenees.