Complex sentence: Assyria retained a stable monarchy, the best army in the world and an efficient civil administration, thus enabling it to survive the Bronze Age Collapse intact and, from the late 10th century BC, it once more began to assert itself internationally.
Split into simpler sentences: Assyria retained a stable monarchy, the best army in the world and an efficient civil administration, enabling it to survive the Bronze Age Collapse intact. From the late 10th century BC, it once more began to assert itself internationally.