The conflicts with surrounding nations to which they were exposed made the Jews concentrate their forces, and so enabled them to wage successful war with nations mightier than themselves. Their heroism under the Maccabees and under Bar-Kochba, in the middle ages and in modern days, permits them to take rank among the most valiant in history. A historian of literature, a non-Jew, enumerates three factors constituting Jews important agents in the preservation and revival of learning:[21] First, their ability as traders. The Phoenicians are regarded as the oldest commercial nation, but the Jews contested the palm with them. Zebulon and Asher in very early times were seafaring tribes. Under Solomon, Israelitish vessels sailed as far as Ophir to bring Afric's gold to Jerusalem. Before the destruction of the Holy City, Jewish communities established themselves on the westernmost coast of Europe. "The whole of the known world was covered with their settlements, in constant communication with one another through itinerant merchants, who effected an exchange of learning as well as of wares; while the other nations grew more and more isolated, and shut themselves off from even the sparse opportunities of mental culture then available." The second factor conducing to mental advancement was the schools which have flourished in Israel since the days of the prophet Samuel; and the third was the linguistic attainments of the Jews, which they owed to natural ability in this direction. Scarcely had Greek allied itself with Hebrew thought, when Jews in Alexandria wrote Greek comparable with Plato's, and not more than two hundred years after the settlement of Jews in Arabia we meet with a large number of Jewish poets among Mohammed's disciples, while in the middle ages they taught and wrote Arabic, Spanish, French, and German--versatility naturally favorable to intellectual progress.