Complex sentence: If the supposition that Alcimoennis belonged to the Vindiliker is correct, then the city may have been abandoned after war with the Germanic Markomann tribe moving in from the north nearly totally destroyed the Vindiliker as a people and left their infrastructure in a shambles.
Split into simpler sentences: If the supposition that Alcimoennis belonged to the Vindiliker is correct, then the city may have been abandoned after war with the Germanic Markomann tribe which moved in from the north. The nearly destroyed the Vindiliker as a people and left their infrastructure in a shambles.