Complex sentence: Galicia was spared the worst of the fighting in that war: it was one of the areas where the initial coup attempt at the outset of the war was successful, and it remained in Nationalist (Franco's army's) hands throughout the war.
Split into simpler sentences: Galicia was spared the worst of the fighting in that war. It was one of the areas where the initial coup attempt at the outset of the war was successful, and it remained in Nationalist (Franco's army's) hands throughout the war.