EXPANSION OF CHRISTENDOM 305 the Guadalquivir in the south, touching the Mediterranean coast a little between Aragon and Granada, and the Atlantic coast at the mouth of the Guadalquivir between Granada and Portugal. Such for over two hundred years remained the political geography of the Spanish peninsula, until the close of the Middle Ages. After Henry I and Otto the Great in the tenth century checked the invaders who had threatened the East Frankish Kingdom from north and east, the Holy Roman German Emperors who succeeded them gave but slight expansion . . r • northeast in attention to the problem of their eastern frontier, the twelfth They were too occupied with Italian projects, centur y with the investiture struggle, and with other problems. When invasions of the Empire by the Slavs forced them to interfere, they usually contented themselves with enforcing a vague recognition of their overlordship from the Slavic princes and perhaps a more substantial payment of tribute, but they made little effort to Christianize or to settle the Slavic territory. It was therefore left to the local lords of the petty states along the eastern border to carry on the work of eastward German colonization. On the whole, not much was accomplished until the twelfth century. Then, under the leadership of the Counts of Holstein, of Albert the Bear, Count of the North Mark (11 34-1 170), and of Henry the Lion, Duke of Saxony, a great advance of the German frontier was made from the Elbe to the Oder, while the Danes made haste to secure the island of Riigen in the Baltic. The previous inhabitants of the region between the Elbe and the Oder, Baltic Slavs in the north and Sorbs in the south, were for the most part either ejected from Displace- their lands or fell to the position of serfs or ™ ent ? f wretched cottagers without any legal title to the German small plots of land which they occupied. The colonists Slavs, whose wooden ploughs merely scraped the surface of the soil, had generally occupied only the more easily culti- vated land, and had left swamps, forests, and thickets unreclaimed. Now German colonists with their superior
