After the fall of Aksum due to declining sea trade from fierce competition by Muslims and changing climate, the power base of the kingdom migrated south and shifted its capital to Kubar (near Agew). They moved southwards because, even though the Axumite Kingdom welcomed and protected the companions of Prophet Muhammad to Ethiopia, who came as refugees to escape the persecution of the ruling families of Mecca and earned the friendship and respect of the Prophet. Their friendship deteriorated when South-Arabians invaded the Dahlak islands through the port of Adulis and destroyed it, which was the economic backbone for the prosperous Aksumite Kingdom. After a second golden age in the early 6th century the Aksumite empire began to decline in the mid 6th century, eventually ceasing its production of coins in the early 7th century. Around this same time, the Aksumite population was forced to go farther inland to the highlands for protection, abandoning Aksum as the capital. Arab writers of the time continued to describe Ethiopia (no longer referred to as Aksum) as an extensive and powerful state, though they had lost control of most of the coast and their tributaries. While land was lost in the north, it was gained in the south; and, though Ethiopia was no longer an economic power, it still attracted Arab merchants. The capital was moved to a new location, currently unknown, though it may have been called Ku'bar or Jarmi.