why did Raleigh and Humphrey invade the Catholic island of Ireland in the 1560s?

Answer 1

Elizabethan England's motivation to pacify Ireland is in response to a four hundred year history with the island at the time and its relatively recent unification with England through the crowns as well as the religious turmoil affecting Europe as a result of the reformation and subsequent counter-reformation.
Henry VIII had made Ireland a kingdom, and established a lord governor to administrate the island to the benefit of the crown.

The Irish at the time were a melting pot of Anglo-Irish who had first colonized the island in the 12th century, Scandinavian vikings, and the native Gaelic Irish (who felt they were descendants from the Spanish). Ireland had been ruled by Gaelic chiefs until Henry VIII created Earldoms and offered a policy known as surrender and regrant to gaelic chiefs to renounce their chieftains and accept an earldom by the king. Although many did this, it is clear in Irish history that the Irish were still rogue from English rule. The later 6th Century is really a turning point in Irish history that begins to suggest a nationalist sentiment among the Irish. The unifying factor for this national identification is religion. Ireland, like England only a generation before was Catholic. Elizabethan England was Anglican. However, their was no Anglican Church at the time and religious strife affected most of Europe during this time. Wars broke out, the Auld Alliance between France and Scotland threatened England and the English felt that the Catholics in Ireland were therefore a liability to the security of England.
The English suffered heavy financial losses administrating their Irish colony. They frequently opted for military intervention including Raleigh, and justified their expeditions as defense of England, securing the Anglican faith from the popists. It was an effort to colonize the Irish and reading primary materials suggests that the English from the first Anglo-Norman invasion in the 12th century were seeking to make the Irish more English.

Irish history is a truly fascinating subject and I recommend reading more on the subject by buying A History of Ireland by Roy, or reading about British history during the Tudor age. I recommend John Guy who is considered the world's foremost authority on the subject as well as Brendan Kane who teaches Irish history at the University of Connecticut.

Answer 2

There were 2 uprisings called the Desmond Rebellions. They were lead by James Fitzmaurice Fitzgerald. These happened around Munster. Humphrey Gilbert was governor of Munster at the time. The first rebellion was in 1569. It was brought down in 1573. The second one was in 1579 and over with in 1580. In the first one, it was mostly Native Irishman. The second one the Irish had help from the Spanish, Italians and the Papacy.