The Division of Sancho III’s Empire and…
1054 CE
The Division of Sancho III’s Empire and the War Between Castile and Navarre (1037–1054 CE)
Upon the death of Sancho III of Navarre, his vast Iberian empire is divided among his sons:
- Ferdinand I receives the County of Castile,
- García III inherits the Kingdom of Navarre.
In 1037, after the death of Bermudo III of León—who dies without heirs at the Battle of Tamarón against Ferdinand—the Castilian count claims the Kingdom of León through his wife, Sancha of León, Bermudo’s sister. Ferdinand enters León in 1038, officially uniting the crowns of León and Castile under his rule.
García’s Expansion and the Taifa Kingdoms
As king of Navarre, García III benefits greatly from the disintegration of the Caliphate of Córdoba and the resulting weakness of the taifa kingdoms. Taking advantage of this, he conquers Calahorra in 1045, further strengthening his kingdom.
Meanwhile, as a reward for his support in the conquest of León, Ferdinand grants García several Castilian territories, including:
- Oca to the gates of Burgos,
- Briviesca to the Urbel Valley,
- Castrobarto to Bricia,
- The Nervión River to Santander.
The Battle of Atapuerca and the Reduction of Navarre (1054 CE)
Relations between the two brothers eventually deteriorate, leading to war between Castile and Navarre. On September 15, 1054, at the Battle of Atapuerca, Ferdinand defeats and kills García III, effectively reducing Navarre to a vassal state under García’s son, Sancho García IV.
At this time, Navarre still includes Álava and La Rioja, traditionally Castilian territories, but Ferdinand only demands the cession of Bureba.
The Gradual Expansion of Castilian Control
Over the following decade, Ferdinand I gradually extends his influence over western Navarre, though peacefully and subtly—a process detectable only in the documentary record, rather than through direct military conquest.
This progressive expansion further strengthens Castile and León, paving the way for its dominance in Christian Iberia in the years to come.