The linguists were the first to study the literary document, inaccurately called the Bavarian Geograph, which is kept in the Eavarian State Library in Munich. This document was studied also by the Bohemian literary historians, especially J. Dobrovský and P. J. Šafařík, followed by others. From the younger generation it was L. Niederle and V. Vaněček. Recently these studies were intensified by the geographer B. Horák, who transferred the names of tribes into a map to enable other research workers easier orientation in the problems. Several German and Polish research workers have also successfully discussed the document. However, even the recent papers show inadequacies in the interpretation of for example the Bohemian beginnings. This is the reason why I am trying to solve some problems concerning Bohemia on the basis of topography and to consider the contents of the geographical and historical document from the point of view of ethnography and demography of the Slavs, especially in the West, at the end of the 1st millennium. The most important conclusions are summarized in the map and in the concluding paragraphs of the paper. According to the first, i. e. the oldest part of the document, dating probably from the second half of the 9th century, I definitely locate the Western Slavonic tribes in the regions along the Baltic coast and the river Elbe. According to the third, i. e. the last part of the Anonymous Geography, probably from the beginning of the 10th century, I can locate the tribes with greatest probability in the region of today's Poland. The middle part of the document remains obscure and unreliable. I consider as most important the statement that the Anonymous Geography was concerned with the Western Slavs from the North to the South, south-east of Denmark, not north of the Danube; the introductory sentence is obviously of the latest date. Equally important and quite new is the method of using the data contained in the document concerning the number of castles of individual tribes to suggest the number of the tribe units. The most powerful union of the Velets-Lutices consisted of about 3/4 million, and there were about 1/2 million people in the tribe of the Serbians along the river Elbe: About 1 million of Slavs lived in the territory of today's Poland. The Scandinavian origin of the Anonymous Geography is proved also by the fact that the historical and geographical document knows hardly half of the Slavonic tribes in the Bohemian countries, having about 1 million of people. This gap is collated and supplemented with the data of the foundation document of the Prague bishopric and of the memoirs of the Arabian traveller Ibrahim ibn Jacob. This man knew four Slavonic countries in the West, existing in the sixties of the 10th century: The Velet, the Polish, the Bohemian and the Bulgarian state. I estimate that there were about 10 million Western and Southern Slavs in the 10th century, which is about half of the total number of the Slavonic people. Towards the end and at the beqinning of the second millennium the Obodrites were the first to succumb in the long fight of the Germans against the Slavs; later even the powerful Velets disappeared from the history. The causes were more complicated and we must look for their explanation not only in christianity and its popularization, but also in economic, trade and administrative conditions; we find similar points in the fate of the Serbians and the Lusatians. The more significant is therefore the development of the ancient Czechs who since the 10th century have held the flag of the Western Slavs the highest. A Russian professor expressed it a long time ago in these objective words: "Of all the Slavs the Czechs deserve the greatest credit."