The second period, therefore, in the record of the conquests of Charles the Great includes the history of the making firm of his new eastern and south-western borders. But this is not, like the first fifteen years of his reign, a time of complete conquest and incorporation of races who were near akin to the Franks. All the Teutonic peoples of central Europe were already gathered beneath the sceptre of Charles; the tribes with which he had now to do were strangers to the Franks, not only in religion, but in blood and language. [Sidenote: Wide scope of Charles’s schemes.] The work of Charles in the East in the second period of his reign was to make the Slav and Avar harmless, by compelling their princes to pay homage and tribute, not by occupying their realms with Frankish garrisons, or carving them up into countships and marches. In the West, on the other hand, his task was to build up a strong border against the Moor, by conquering, one by one, the fortresses between the Pyrenees and the Ebro. The Moslem had to be driven out, since there was no hope of converting him. In the towns from which he was expelled a new population grew up, neither purely Spanish nor purely Frank, but the mixed race of the Catalans, in whose veins Romano-Spanish, Visigothic, Aquitanian, and Frankish blood was mingled in various proportions, so that they have always differed very considerably, both in character and in language, from the inhabitants of the rest of the peninsula. But the history of the foreign policy of Charles during the second period of his reign contains much more besides his dealings with the Slav, the Moor, and the Avar. He had frequent troubles with the East-Roman Empire, arising from their disputed boundaries in Italy. In the very end of his reign he met and turned off the first assault of the Danes on the Frankish realm, an attack insignificant in itself, but portending the gravest dangers in the future. We find him interfering beyond the British sea with the affairs of Northumbria, and at the same time extending his hand far to the south to seize the Balearic Isles. Even to the distant Abbasside Caliph at Bagdad his fame was known, and Haroun’s ambassadors sought the court of Aachen to concert an alliance with him.