Early Russian chronicles describe the Letts and Lithuanians as divided into several tribes.[87] The Yatvags were scattered along the banks of the Narev. The Lithuanians proper together with the Shmuds peopled the Niemen valley. Very little dialectical differences exist between the two. The Shmuds cluster now in northwestern Kovno without, however, attaining the Baltic shore. The left bank of the Drina was occupied by the Semigals, while on the right dwelt the Letgols who were the ancestors in direct line of the Letts of southern Livonia. The Kors, who lived on the western shores of the Gulf of Riga, were later to impose their name on the province of Kurland.[88] Two of these tribes, the Shmuds and the Lithuanians, escaped the Teutonic conquest through the inaccessibility of their forested and marshy retreat. Around them the Kors and the Letts, as well as the primitive Slav occupants of Prussia, had been subjugated by the Knights of the Teutonic Order. The only salvation for these tribes from Teutonic oppression consisted in their seeking the natural shelter occupied by the two more fortunate groups of their kinsmen. Behind this natural barrier Lithuanian nationality was born in the middle of the thirteenth century under the leadership of Mindvog, an energetic chieftain who insured his own supremacy by causing the leaders of rival clans to be put to death. With the help of the Poles the Lithuanians eventually checked the easterly expansion of the Teutons. The region occupied by Lithuanians in former times can be traced today by the distribution of the type of dwelling peculiar to this people. The ancient area exceeds the borders of the present linguistic zone. The earliest examples of Lithuanian houses consist of a single room. The indoor life of a single family was spent within this one apartment. This primitive habitation grew into the modern style by the successive addition of rooms. In course of time a kitchen or a stable was added to the main building. Sometimes the old type of house stands to this day adjoining more modern buildings. In such cases it is used as a barn.