Thus, we see, the process of expansion towards the north, east, and south may be described as a spontaneous movement of the agricultural population.  It must, however, be admitted that this is an imperfect and one-sided representation of the phenomenon.  Though the initiative unquestionably came from the people, the Government played an important part in the movement.

In early times when Russia was merely a conglomeration of independent principalities, the Princes were under the moral and political obligation of protecting their subjects, and this obligation coincided admirably with their natural desire to extend their dominions.  When the Grand Princes of Muscovy, in the fifteenth century, united the numerous principalities and proclaimed themselves Tsars, they accepted this obligation for the whole country, and conceived much grander schemes of territorial aggrandisement.  Towards the north and northeast no strenuous efforts were required.  The Republic of Novgorod easily gained possession of Northern Russia as far as the Ural Mountains, and Siberia was conquered by a small band of Cossacks without the authorisation of Muscovy, so that the Tsars had merely to annex the already conquered territory.  In the southern region the part played by the Government was very different.  The agricultural population had to be constantly protected along a frontier of enormous length, lying open at all points to the incursions of nomadic tribes.  To prevent raids it was necessary to keep up a military cordon, and this means did not always ensure protection to those living near the frontier.  The nomads often came in formidable hordes, which could be successfully resisted only by large armies, and sometimes the armies were not large enough to cope with them.  Again and again during the thirteenth and fourteenth centuries Tartar hordes swept over the country—­burning the villages and towns, and spreading devastation wherever they appeared—­and during more than two centuries Russia had to pay a heavy tribute to the Khans.

Gradually the Tsars threw off this galling yoke.  Ivan the Terrible annexed the three Khanates of the Lower Volga—­Kazan, Kipttchak, and Astrakhan—­and in that way removed the danger of a foreign domination.  But permanent protection was not thereby secured to the outlying provinces.  The nomadic tribes living near the frontier continued their raids, and in the slave markets of the Crimea the living merchandise was supplied by Russia and Poland.

To protect an open frontier against the incursions of nomadic tribes three methods are possible:  the construction of a great wall, the establishment of a strong military cordon, and the permanent subjugation of the marauders.  The first of these expedients, adopted by the Romans in Britain and by the Chinese on their northwestern frontier, is enormously expensive, and was utterly impossible in a country like Southern Russia, where there is no stone for building purposes; the second was constantly tried, and constantly found wanting; the third alone proved practicable and efficient.  Though the Government has long since recognised that the acquisition of barren, thinly populated steppes is a burden rather than an advantage, it has been induced to go on making annexations for the purpose of self-defence, as well as for other reasons.