The northeastern section of Moravia is known as the Lassko country and is peopled by Lassi Moravians. This group occupies districts mainly around the towns of Moravska-Ostrava and Frydland. South of them a number of Slovak villages are found within the Moravian border. Their inhabitants, sometimes known as Moravian Slovaks, are emigrants from the Hungarian mountains who reached the western Carpathians in the eleventh and twelfth centuries. Although they speak Bohemian, their customs differ considerably from Bohemian usages. The balance of Moravia is peopled by Hanaks, who are easily distinguished by temperamental differences from the previous two groups. The Hanaks as a rule are calm and inclined to ponderous ways of thought and action, whereas both the Lassi and Slovaks are quick-minded and lively. German expansion into Moravia is facilitated by the valley of the March, which penetrates into the heart of the Margravate. The Elbe and Moldau in Bohemia play a similar part as agents of Germanization. As in Bohemia, the Germans are confined to the border heights or the towns. In the thirteenth century many German fortified towns existed in Moravia. The rise of a powerful German middle class dates from this period. Intellectually as well as industrially the Teuton element is the more advanced. Racial and linguistic differences are accentuated by religious antagonism, the German element being Roman in creed. The clergy in fact have acted as a powerful agent of Germanization in Moravia. The Slovaks are dwellers of the northern highland border of Hungary who reached Europe in the sixth century B.C. They are closely related by racial and linguistic affinity to the Bohemians and Moravians. The course of centuries has failed to change their customs or the mode of life they led in the western Carpathians. The Hungarian plain spread out below their rocky habitation without tempting them to forsake the huddled conditions of their native valleys. Their language holds its own as far east as the Laborec valley. Junction with Polish is effected in the Tatra. Once only in their history did the Slovaks succeed in creating a great nation. In 870 A.D., under the leadership of Svatopuk, they established the short-lived Great Moravian Empire. Unfortunately his successors were unable to maintain the independence of the nation he founded and the empire crumbled to pieces before the repeated attacks of the Hungarians. By the tenth century the political ties between Bohemians and Slovaks were completely severed.