Sancho III’s Expansion and War Against León (1030s CE)

Following the succession of Bermudo III to the throne of León, Sancho III of Pamplona strengthens his influence over Castile and León by arranging the marriage of his son, Ferdinand of Castile, to Sancha of León, the sister of Bermudo III and the former fiancée of the assassinated Count García Sánchez of Castile.

As part of the marriage alliance, Ferdinand receives a dowry that includes contested Leonese lands, further expanding Castilian control.

War with Bermudo III and the Occupation of León

Tensions between Sancho III and Bermudo III quickly escalate into full-scale war. Sancho, commanding combined Castilian and Navarrese forces, launches a military campaign against León, swiftly overrunning much of the kingdom and occupying Astorga.

By March 1033, Sancho III’s dominion extends from Zamora to the borders of Barcelona, marking the height of his power and making him the most dominant Christian ruler in Iberia at the time.