Complex sentence: Taking advantage of the Romans' problems, he extended Visigothic power in Spain, driving the Suevi into the northwest of Iberia, and by the time the Western Empire ended in 476, he controlled nearly the entire Iberian peninsula.
Split into simpler sentences: Taking advantage of the Romans' problems, he extended Visigothic power in Hispania, driving the Suevi into the northwest of Iberia. By the time the western Empire ended in 476 he controlled nearly the entire Iberian peninsula.