The area of foreign policy where Philip seemed to achieve the most success was in his exploitation of the political situation in Portugal which led to Portugal being added to Philips monarchia. Portugal was already in a fragile state after the death of King Sebastian in 1578 the throne of Portugal had been given to his sick and aged Uncle Henry due to Sebastian having no children. This left many worries over who would be Henrys successor and eventually by 1580 Philip was King of Portugal.
Philips was successful in Portugal due to his two pronged policy of diplomacy and bribery along with the dispatching of Granville, one of his closest advisors to cultivate merchants of Lisbon who already were closely identified with Philip due to loans from the crown. This detailed and precise approach successfully ensured the withdrawal of Catrina Philips main rival in Portugal. Furthermore despite the crowning of Don Antonio as King of Lisbon, Philip was very successful in invading due to his awareness of Portugals army being depleted from expeditions to Morocco.
Another area of Philips foreign policy where he achieved a high amount of success is his neutralisation of the Turks as a threat in the Mediterranean. Since the early 16th century the Turks had been attempting to expand their empire into Europe, forcing Philip to react. However despite later success, at first Philip was very unsuccessful against the Turks due to surprise assaults from the Turkish fleet along with blockades and poor weather. On the other hand, Philip made these early setbacks irrelevant in 1571 when alongside the Holy League he successfully defeated the Turks in Lepanto. This was seen as making Philips foreign policy particularly successful due it being seen as the greatest victory for the Christian empire, and thus had a huge religious impact.
However, Philips greatest success when dealing with the Turks seems to be the negotiating of a truce in 1578. Despite the negative repercussions at the time involved with Philip putting his own problems before religion, the truce was highly successful as it allowed Philip to have little need for substantial military involvement in the Mediterranean, allowing him to move his armies further north in order to deal with the Netherlands and also his aspirations in France and England. This truce can be seen as having a negative impact on Philips prestige due to the agreement being a sign that he had backed down and was inspired for fighting for Catholicism as his title champion of Catholicism would suggest. However, its political benefits easily outweigh the impact it has on Philips prestige and overall was one of Philips most successful decisions in his foreign policy.
One area where Philip achieved little success was in the last 15 years of his reign where he seemed to change his foreign policy to being that of an aggressive imperialist, this appeared to be due to the fact that he spread his armies to thinly, fighting on three fronts at once in the 1590s. Problems with England began through Elizabeths fears of England being turned Catholic as she could see what was happening in the Netherlands. These fears led to Elizabeth signing the treat of Nonesuch with rebels in the Netherlands, providing them with money and soldiers.
In response Philip ordered the Armada to invade England in 1588 and despite this limiting English interference in Netherlands it was fairly unsuccessful due to Philips plan being highly complicated, furthermore the two fleets he sent had no co-ordination between them, and the as the Spanish fleet did not possess heavy artillery it was outgunned by the English. Philip did launch two more Armadas in 1596 and 1597, however these achieved even less success due to weather and didnt even reach England, furthermore these crippled Spain financially due to the sheer amount of money each Armada cost to construct.
Similarly in France Philip achieved little success and moreover due to his actions in France he actually contributed to the success of the Netherlands revolt. After many years of civil war and attempted interventions by Philip to turn France Catholic, Henry of Navarre, an anti Spanish protestant was crowned King of France. In response Philip ordered the transferral of troops from the Netherlands to attack France in a bid to claim the thrown for his daughter Elizabeth of Valois. Despite Henry becoming a Catholic, Philips attack on France was highly unsuccessful and led to his third bankruptcy in 1596 and the removal of troops from the Netherlands during vital points of the revolt stopped victory against the rebels.
Overall Philips foreign policy seemed to be successful early on in his reign due to him being defensive and reactive up to 1584 as it gained him Portugal and eliminated the threat of the Turks. However after 1584 Philip seemed to change to being an aggressive imperialist possibly due to the fact he wanted to leave behind some kind of impact as he realised he would not have long left as King, however this was unsuccessful as he tried to do to much in a short period of time, leaving his armies spread too thinly without enough equipment due to his mounting financial problems.