Complex sentence: The Romans failed to take advantage of the immense wealth they possessed and this resulted in frequent border raids, forcing the Romans to build extensive fortifying walls along much of their borders and mobilize a large military from all Roman provinces.
Split into simpler sentences: The Romans failed to take advantage of the immense wealth they possessed. This resulted in frequent border raids, forcing the Romans to build extensive fortification walls along much of their borders and mobilize a large military from all Roman provinces.