Answer the following question: Given the following passage  "A few centuries later, coinciding with the first waves of the invading Germanic peoples (Suevi, Vandals and Alans, and later the Visigoths) and the power vacuum left by the demise of the Roman imperial administration, the church assumed the reins of power in the city and replaced the old Roman temples with religious buildings. With the Byzantine invasion of the southwestern Iberian peninsula in 554 the city acquired strategic importance. After the expulsion of the Byzantines in 625, Visigothic military contingents were posted there and the ancient Roman amphitheatre was fortified. Little is known of its history for nearly a hundred years; although this period is only scarcely documented by archeology, excavations suggest that there was little development of the city. During Visigothic times Valencia was an episcopal See of the Catholic Church, albeit a suffragan diocese subordinate to the archdiocese of Toledo, comprising the ancient Roman province of Carthaginensis in Hispania.",  answer the following question. Note that the answer is present within the text.  Question: When did the city attain military importance
Answer:
After the expulsion of the Byzantines in 625