Complex sentence: As the Idirans were religiously committed to holding on to all of their conquests, these strikes forced them to divide their attentions, and they were eventually overwhelmed by the Culture, a civilization they had not considered as having the requisite will to fight.
Split into simpler sentences: As the Idirans were religiously committed to holding on to all of their conquests, these strikes forced them to divide their attentions. They were eventually overwhelmed by the Culture, a civilization they had not considered as having the requisite will to fight.