Pope Pius V
In the sixteenth century, the western world centred on Europe. America had only recently been discovered and was a land for adventurers and explorers to conquer and discover and bring back to Europe all kinds of wonders such as potatoes and tobacco. It was not a developed country architecturally or economically. The most important person in Europe was arguably the Pope who resided then, as now, in the Vatican at Rome. Roman Catholicism was still the dominant European religion and the Pope, as its head, wielded enormous power in Roman Catholic countries. Even in non-Roman Catholic countries such as England, the Pope had a great influence amongst those still adhering to the Roman Catholic faith.
The most powerful ruler, however, was Philip II of Spain. His father, Charles, had been one of the most powerful men ever to have lived in Europe. Not only was he King of Spain, but also governor of the Netherlands and Holy Roman Emperor, a very prestigious title indeed. Philip inherited the throne of Spain aswell as the Netherlands, was King of Portugal for a while, and owned lands in the Americas that were a source of great wealth. Unlike his father, Philip made Spain his central home and under his rule, Spain was at the height of its influence and recognized as the most powerful country in Europe, if not the world.
However, relations between Philip and his neighbours were poor. He was constantly in conflict with France, mismanaged the government of the Netherlands to the extent that there was open rebellion and eventual war there, and he came into conflict with Elizabeth. The powers of Europe were wary of Philip and Queen Elizabeth in particular tried to keep in check his wealth, and the potential threat Catholic Spain posed to Protestant England, by discretely authorizing her sailors to pirate his ships as they came from America. William Cecil, the Queen's chief minister, did not approve of this, so Elizabeth tried to keep knowledge of what was going on from him. Not only did capturing a Spanish ship laden with treasure improve her finances, but it depleted Philip's in the hope to stall his often threatened invasion of England, his so called "Enterprise of England."
For details on The Enterprise of England see the section on The Armada
England and Spain were officially at war in 1585 after years of underhanded conflict, and the war lasted until the Queen's death. Philip died in 1598, but his son, Philip III, continued the war, even though he did so half heartedly. He saw the conflict between Elizabeth and Philip as just that, a clash of personalities, and in many ways perhaps that was the case.