Alfonso I of Aragon did not earn his nickname by sitting still. As the Almoravid empire, the Berber power that had swept up from North Africa to dominate Muslim Iberia, fell into decline almost as fast as it had risen, Alfonso pressed his advantage hard. He took Zaragoza in 1118, then Calatayud and Daroca by 1120, pushing the frontier of the Christian kingdoms deep into contested ground. He was a king who understood that a weakening enemy was an opportunity, and he spent his reign turning that understanding into conquest after conquest across the valley of the Ebro and beyond.

The empire Alfonso faced had itself been an outsider once. The Almoravids were a Berber movement that had swept north out of the Sahara and Morocco decades earlier to unite Muslim Iberia under a single banner, halting the Christian advance for a time and ruling their vast realm from Marrakesh. But a power built on rapid conquest can unravel just as fast as it rose. By the 1120s the Almoravids were loosening their grip on the distant Iberian provinces they had gathered, strained by the sheer reach of what they held. It was into that weakening that Alfonso drove his campaigns, reading the decline correctly and pressing on it without mercy. The army sent to hunt him in 1129 was, in a sense, an attempt to prove the empire still had teeth.

In 1128 Alfonso carried the war into the land of Valencia itself, striking into the heart of Almoravid territory in the east, the region Muslim geographers called Xarq al-Andalus. This time the Almoravids answered in force. They summoned a powerful army newly arrived from deep in Morocco and merged it with the African cavalry of the governor of Seville, assembling the combined host for the express purpose of running down the Aragonese king who had troubled them for so long. It was less a defense of a border than a manhunt on the scale of an army, aimed at ending Alfonso and his ambitions in a single campaign.

The two forces met at the Castle of els Alcalans, a stronghold in the hills of the interior near the modern town of Montserrat, southwest of the city of Valencia. The clash is remembered by two names, the Battle of Alcala and the Battle of Cullera, tying it to the coastal country that stretches toward the mouth of the Xuquer. When it ended, the hunters had become the hunted: the Aragonese carried the day, and the army sent to destroy Alfonso was itself broken on the Valencian hillside. The Battler had turned the trap against those who set it. For Alfonso, it was one more vindication of a career spent betting against a fading power.

The consequences outran the battlefield. The Valencian Muslim chronicler Ibn al-Abbar, looking back on the event, judged that the Almoravids' disastrous defeat cost them their standing in Xarq al-Andalus. Their authority, once feared, began to lose its grip on the people it ruled. In time that erosion helped open the way for a second age of taifa kingdoms, the small independent Muslim states that fractured the region from the 1140s, reaching Valencia around 1145. A single lost battle at an obscure hilltop castle did not topple an empire on its own, but it exposed how brittle Almoravid power had become, and the cracks it revealed only widened from there.