Traditional historiography pegged him as basically Philip II's dumbass son, the opposite to his forceful and ambitious dad, to the point the old Philip himself famously bemoaned in his deathbed that he was leaving an awful successor for the greatness of his kingdoms; he had always considered his prodigy daughter Isabella Clara Eugenia his true heiress, but the throne had to fall with force on her untalented half-brother for being the male.note This is not a lie: Philip III turned out to be an apathetic, unfocused king, maybe even a reluctant one, who preferred others to rule on his place and was not even good at handpicking them, which undoubtedly brought all sorts of present and future problems and marked him very negatively when compared with his predecessors. Modern perspectives have argued for a more nuanced image, though, conceding that Philip the Third was sincerely trying to do his best with his limited options and actually managed to achieve a decent respite for the weary Hispanic Monarchy, all in a convoluted time that would have proved a challenge for much better rulers.
Philip was a contrasting successor to Philip II's first son and original heir, Charles, an immensely brainy, ambitious prince with the insignificant caveat of being an utter psycho, which ultimately got him dying in prison after an attempt on the life of his uncle John of Austria (all because John refused to help him revolt against the kingdom). Although Philip III had the advantage of sanity over Charles, he had neither the interest nor the ability to reign — he was way more drawn to religion, art, games, dancing, hunting, parties, and just everything but taking the reins of the kingdom. Due to this, as soon as he was sitting in the throne, he reached for a friend he considered more capable than himself, Francisco de Sandoval y Rojas, Duke of Lerma, and appointed him valido, a sort of regent or prime minister that would essentially reign (hopefully well) in his place. This decision, while rooted in actual political theories against monarchical personalism that were emerging in Europe as a reaction to Niccolò Machiavelli, was probably a giant act of escapism from the overwhelming pressure of inheriting a gigantic empire he knew would not be able to handle, and it instantly gained the antipathy of his subjects, who rightfully condemned Philip as a weak-willed slacker. In reality, delegating in someone more skilled was not new in European politics and should have been Philip's best decision possible... had him chosen the right man, which turned out not to be the case at all.
It turned out the Duke of Lerma was corrupt to the bone and basically capitalized on his position to enrich himself. In the biggest (but far from the only) of his misdeeds, he advised Philip to move Spain's capital from Madrid to Valladolid, where casually Lerma owned massive amounts of state, and then moved it back to Madrid six years later after acquiring equally large Madridian lands, sealing a monumental con that made Lerma the richest man of the empire at the expense of endless economical and administrative turmoil. When Philip married his cousin Margaret of Austria, a skilled politician herself, she quickly realized where was the trouble and tried to oppose Lerma in everything she could, but little could be done about it yet because Philip trusted him. Worse enough, the lack of a strong source of leadership in Madrid had the side effect of unintentionally decentralize power in the extents of the empire, producing the so-called "imperial proconsuls", governors and generals that were either allowed or forced to operate on their own devices with various results. In a way, it's believed this was actually what Philip desired, as he was an adherent to the new politics referred above, which spoused a government based on councils, a greater involvement of higher noblemen, and more free time for himself, but the result was a veritable mess that couldn't achieve the results they wanted.
While it is tempting to blame Philip for remaining unaware of those problems, modern science has shown he might have not been merely trapped in an escapist circuit. Judging by the chronicles of his antics, where he gambled compulsively and lost gigantic amounts of money to his friends, it has been proposed Philip was affected by a heavy case of ludomania, probably mixed with a clinical depression and possibly some neurological condition related to his family's high consanguinity. It is also confirmed, as stated by the king's own tutor Jehan de L'Hermite, his father Philip II, and his aunt the Holy Roman Empress Dowager Maria, that the Duke of Lerma was acting as a Toxic Friend Influence over the Third for all of their life together, fueling his distractions and addictions in order to have him out of his way. Some even believe that moving the court away from Madrid was also a way to try to keep Philip away from the more positive influence of Empress Maria, who lived in the Convent of Las Descalzas Reales; he only moved the court back to the city when she died.
Philip had inherited an empire simultaneosly at war with England and the Dutch rebels, and barely avoided being in another war with France after Philip II's otherwise suicidal involvement in the French Wars of Religion managed to quell things with Henry IV. Initially, the Third believed that a big last push was all Spain needed to solve the conflict, so his government initiated an attempt to relieve the Catholic Ireland against England and deployed the new general and proconsul Ambrogio Spinola to recover the ground lost to the Dutch. The expected victory kept evading the Spaniards, but James V Iand I's ascension to the English throne and Spinola's success at stalemating the rebels offered the opportunity of moving the conflict to the negotiation table, and Philip, less inclined to glorious holy war to death than his father, didn't waste time to seize it. His ambassadors put an end to the war with England in exchange for their maritime support against the Dutch, and although this was still insufficient to defeat the rebels, those eventually opened to diplomacy too, concluding in the Twelve Years' Truce. In Spain, this truce was seen as teeth-clenching, as it equated to acknowledging the independence of a Dutch Republic, but it still gave Philip and the governor of the Netherlands, Isabella Clara, much needed time to treat other internal problems and generally rebuild things.
During this truce, diplomatic letters from the Tokugawa Shogunate reaching Spain. Trying to mend the Christian-killing debacle happened during Toyotomi Hideyoshi's rule, Tokugawa Ieyasu proposed to build commercial ties between Japan and the Spanish Empire, offering them to allow Spanish cities in his territory in exchange for Iberian science and crafts, which they would use particularly for joint explotation of the Japanese silver mines. Another embassy, sent by Date Masamune with Ieyasu's acquiescence, made similar promises. However, Philip and his ministers declined on the belief that a complicated deal in which Japan would gain much more than Spain was dangerous for their regional interests, especially given that Ieyasu himself would soon start persecuting Christians himself and becoming closer to Spain's Dutch enemies. Spies suspected a Dutch-Japanese invasion of the Spanish Philippines was in the making, but it seems the Shimabara Rebellion and the project's whole cost crashed it.
Another peacetime adjustment, and in one of the few times Philip heeded the advice of someone who actually deserved it, involved handing Pedro Téllez-Girón, Duke of Osuna and grandson-in-law to Hernán Cortés, the jobs as Viceroy of Naples and Sicily that he desperately wanted. The Italian territories were in a state of military and civil decadence, plagued by corruption and turned into easy prey for Muslim pirates and slavehunters, but the Duke of Osuna, a capable administrator and veteran of the European wars, quickly reversed the situation, re-establishing order and reforming the local fleets until those became the biggest fish of the pond. Osuna's mandate brought multiple victories against the Ottomans and Venetians, such as Cape Celidonia, Cape Corvo and Ragusa, and his liuetenant Octavio de Aragón came to the extent of infiltrating and bombarding Constantinople of all places, marking the first and last time in centuries the Ottoman capital was compromised.
Speaking of Muslims, Philip's and Lerma's attempts to mend the economy soon found a different problem with the Moriscos, descendants of Moors converted to Christianity in past times who kept a lot of their customs. Social tension surrounded them, as a significant number were still secretly practicing Islam, and small sectors even went to the extent to serve as spies and supporters of Muslim piracy and Ottoman advances on Spanish coasts. Years earlier, Philip II's attempts to further Christianize them had caused the Rebellion of the Alpujarras, where John of Austria had been forced to act to repress a bloody uprising of Moriscos in open alliance with the Ottomans, and this debacle, mixed with the religious and political tenor of the times, led Lerma to propose the total expulsion of all Moriscos from the Iberian Peninsula. The project was met with shock, as few Christians of any status in Spain wanted to go that far and many of them called for simply working harder to integrate the Moriscos into the Christian community, but it seems this was a rare topic where the Duke of Lerma and Queen Margaret agreed, and so Philip eventually gave his blessing. The expulsion did ultimately more bad than good, as although it was far from the disaster later historiography made it look like, it still caused huge losses of labouring workforce in the lands of Valencia and Aragón, not to talk it only served to alienate and turn many ex-Moriscos into pirates and desperadoes.note
From this point, however, the Duke of Lerma faced an increasing number of court enemies and people who had simply caught on his incompetence; those included his own son Cristóbal de Sandoval, Duke of Uceda, and the royal confessor Friar Luis de Aliaga. To worsen things, imperial proconsuls here and there were capitalizing on it to wage private wars against the Venetian Republic and the Duchy of Savoy, and as if this was not bad enough, the death of King Henry IV of France turned southern Europe into a mess. Momentarily, the crown patched things up with France by double Altar Diplomacy, marrying off Philip's daughter Ana of Austria to the new king Louis XIII and his son Philip to the princess Isabel of Bourbon, as well as signing a peace treaty with Venice and Savoy. However, by this point even Philip, broken by the recent death by childbirth of the queen (rumor is that Lerma has her poisoned, although it's considered rather unlikely), had lost confidence on his supposed friend and would not protect him anymore.
In an event known as the Revolt of the Keys, the Duke of Lerma was finally kicked out of his job in 1618 and spent the rest of his life in a revolving door job as a church cardinal, and his fall accidentally took with him the trusty Duke of Osuna, who happened to have been elected viceroy under his management. Lerma's son and Aliaga were ready to succeed him as validos, but the disappointment with Lerma served to make Philip realize he had seriously screwed up by handing away his throne in the first place and not listening to his wife back when she was alive. From then, he involved himself much more in his job, lamenting to have led such a superficial life up to that point, and never remarried. It was too late, though, as he would only have three more years to live. His last action in politics was to enter the Thirty Years' War as an ally of his uncle Ferdinand of the Holy Roman Empire, whose election as emperor he supported, even although Philip, clearly trying to overcompensate, had also toyed with the crazy idea of trying to make his son and heir Philip emperor like their ancestor Charles V (a bid rejected by the German nobility, who would have died before electing a Spanish born emperor regardless of his bloodline).note He then died prematurely at 43 of a painful illness, days before a meeting with the Duke of Osuna to decide the latter's fate, and the throne was inherited by his son under the name of Philip IV.
A bizarre legend of French origin attributes Philip's death to his court's excessive and uptight etiquette, claiming that Philip actually died of overheat from his chambers' fire because a series of increasingly ridiculous formalities impeded him from just standing away from the hearth when it became too hot. It should go without saying there is no basis for such insanity, although it definitely speaks miles about the reputation the pious king ultimately went to leave.
In fiction
Live-Action TV- He appears briefly in The Ministry of Time, played by Federico Aguado.
