El Burgo de Osma-Ciudad de Osma is a municipality in Soria, Castilla y León, characterized by its historical and strategic importance, based on its orography and defensive infrastructure. This city, located in the valley of the Ucero River, was located in a natural corridor that facilitated the control of the accesses to the valleys of the Ucero and Abión rivers. Its elevated and steep location provided a natural defense, which allowed the construction of fortifications that played a crucial role during the Middle Ages, particularly during the Reconquest.
The castle of Osma, one of the most important fortifications in the region, was built in 930 by order of King Ramiro II of León to defend against the Caliphate of Córdoba led by Abderramán III. The fortress, located on a hill of difficult access, served as a bulwark for the defense of the Christian territories. It was composed of three walled enclosures adapted to the rugged geography of the terrain. It used materials from the ancient city of Uxama, which symbolizes a historical continuity with the Celtiberian and Roman past of the region. At the top of the hill there are still remains of the inner enclosure, including the access gate, high walls and two towers, one of them the keep.
Despite the solidity of its construction, the castle suffered significant damage during the War of the Spanish Succession in the 18th century, when part of the wall was almost blown away to prevent it from being used by enemy troops. In addition, the fortress was used as a quarry, which contributed to its deterioration. Even so, the Torre del Agua, at the base of the hill next to the Ucero River, is preserved as part of the outer defensive system.
In addition to the castle, El Burgo de Osma was protected by walls, built in 1458 by order of Bishop Pedro de Montoya. These walls surrounded the urban center and defended the city from possible attacks. Although a large part of them was demolished in the 18th century, some sections are still preserved, such as the Arco del Cubo and a walkway parallel to the road to La Rasa. The walls, the castle and the watchtowers formed an integral defensive complex that protected the city during the medieval battles.
A fundamental part of the defensive system of the city were the watchtowers or watchtowers. These towers, used during the Reconquest, allowed constant surveillance of the territory and rapid communication by means of smoke or fire signals. Among them, the watchtower of Uxama, located on the hill of Castro, stands out. Built during the Muslim period, its main function was to watch over the castle of Osma and to form part of the extensive defensive network of the Duero River. From this watchtower other strategic points can be seen, such as the castle of Gormaz and the Cañón del Río Lobos.
El Burgo de Osma witnessed important clashes during the border wars between Christians and Muslims. One of the key events was the battle of Osma or Barranco in 939, in which the Christian troops, led by King Ramiro II of León and Count Fernán González, defeated Caliph Abderramán III, marking a turning point in the war for control of the Duero border. This victory consolidated the Christian position in the region and strengthened the defenses of Osma.
Another important battle for the region was the legendary battle of Calatañazor in the year 1000, located about 20 kilometers from El Burgo de Osma. In this battle, a coalition of Christian troops defeated Almanzor, the Muslim leader, which marked the beginning of the decline of the Caliphate of Córdoba. Although Almanzor survived the battle, he became seriously ill and died shortly thereafter, which destabilized the Caliphate and facilitated the Christian repopulation of the region.
With the fall of Muslim power and the death of Almanzor, the population of Osma began to move from the castle hill to the plain, settling in what is now the town of Osma, on the right bank of the Ucero River. This repopulation process was driven by the Christian kings, who saw Osma as a key stronghold to ensure control of the region during the consolidation of the Christian frontiers.
As the region was pacified and the border struggles ceased, the defensive structures of El Burgo de Osma lost their military importance. Nevertheless, the remains of the castle, walls and watchtowers still stand as witnesses to its strategic and defensive past.
Here we see an outstanding example of how geography and medieval defensive architecture combined to protect an enclave of great importance during the border wars between Christians and Muslims. Despite the loss of some of these fortifications, their legacy lives on in the landscape and history of the region, representing a tangible connection to its military and strategic past.
