Complex sentence: The origins of Spanish nationalism have been claimed to have begun with the "Reconquista"-beginning with the victory of Catholic forces against Muslim Moor forces in Granada in 1492 that resulted in a surge patriotic sentiment amongst Catholic Spaniards.
Split into simpler sentences: The origins of Spanish nationalism have been claimed to have begun with the "Reconquista"-beginning with the victory of Catholic armies against Muslim Moor occupiers in Granada in 1492. This resulted in a surge patriotic sentiment amongst Catholic Spaniards.