Complex sentence: In the mountainous, rural northern regions to the north, the Christian rulers were regaining their footing, despite numerous internal conflicts, and they slowly expanded their control throughout the Reconquista, between the Battle of Covadonga c.720 CE and the Fall of Granada in 1492.
Split into simpler sentences: In the mountainous, rural northern regions to the north, the Christian rulers were regaining their footing, despite numerous internal conflicts, and they slowly expanded their control over a period of centuries in a process known as the Reconquista. The Reconquista spanned approximately 770 years between the Battle of Covadonga c.720 CE and the Fall of Granada in 1492.