A marriage between the queen of Castille and the king of Aragon.
As a general answer, the Christian Kingdoms of northern Spain (Castille, Leon, Portugal, Aragon, etc.) wished to drive the Muslims out of Spain. These kingdoms eventually consolidated (except Portugal) into the Kingdom of Spain, led by Queen Isabella of Castille and King Ferdinand of Aragon, who made it their mission to remove the last Islamic Kingdom of Granada and expel all Muslims from Spain with the Inquisition.
Queen Isabella of Castille and King Ferdinand of Aragon. Although, admittedly, the Muslims were ruling very little area in Iberia by that point. Additionally, up to 1480, the Nasrid Emirate of Granada was an ally of Castille that Isabella chose to betray.
Actually Isabel and Ferdinand did not "Unite" anything. Ferdinand II was the King of Aragon. Isabela I was the Queen of Castile and Leon. They were married in 1469. Each ruled their own kingdom(s) and co-ruled their spouse' kingdom. Both were deceased by 1516. Spain did not come into being (was "United") until their Grandson Carlos I of Spain, also known as Charles V of the Holy Roman Empire, inherited the 3 kingdoms in 1516. Isabela I and Ferdinand II never ruled "Spain". Isabela I died in 1504 and was succeeded by her daughter, Juana la Loca (Juana the crazy, who was in turn succeeded by Philip I. Ferdinand ruled Aragon until his death in 1516.
Isabella of Castile-Leon and Ferdinand of Aragon defeated the last of the Moors, then evicted them and the Jews. They DID NOT unite the three kingdoms. Isabella and her descendants remained the only monarchs of Castile-Leon and Ferdinand and his descendants were the only monarchs of Aragon. Carlos I of Spain, their grandson, inherited all three kingdoms in 1516. Carlos I of Spain was also know as the Holy Roman Emperor Charles V. That was the genesis of modern Spain.
Spain became a political entity when Carlos II inherited both the kingdoms of Castile/Leon and Aragon. That was the first time all the territory was under one monarch.
When Columbus made his famous voyages, he was sponsored by Queen Isabella I and King Ferdinand II, who ruled the united kingdoms of Castile and Aragon in Spain.
One country cannot exist inside another. There are no other countries in Spain.
It led to the creation of Spain.
The Christian kingdoms in 1140 were Leon, Castile, Navarre and Aragon. Leon was an expanded version of the Kingdom of Asturias which had conquered lands to its south and repopulated them. Leon was chosen as the new capital and the kingdom was renamed in 866.
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The peace with King Ferrante of Naples was made by King Ferdinand II of Aragon in the late 15th century. This agreement was part of a broader strategy to stabilize relations in Italy and secure the Aragonese interests in the region. The Treaty of 1486 helped to establish a temporary truce between the two kingdoms, allowing for a period of relative peace in southern Italy.
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