Germany, crowded in among three powerful neighbors like France, Russia, and Austria, has had no choice about maintaining a strong standing army and impregnable frontier defenses. The location of the Central European states between the Baltic and the Balkans has exposed them to all the limitations and dangers arising from a narrow circle of land neighbors. Moreover, the diversified character of the area, its complex mountain systems, and diverging river courses have acted as disintegrating forces which have prevented the political concentration necessary to repel interference from without. The Muscovite power, which had its beginning in a modest central location about the sources of the Dwina, Dnieper and Volga, was aided by the physical unity of its unobstructed plains, which facilitated political combination. Hence, on every side it burst through its encompassing neighbors and stretched its boundaries to the untenanted frontier of the sea. Central location was the undoing of the Transvaal Republic. Its efforts to expand to the Indian Ocean were blocked by its powerful British rival at every point--at Delagoa Bay in 1875 by treaty with Portugal, at Santa Lucia Bay in 1884, and through Swaziland in 1894. The Orange Free State was maimed in the same way when, in 1868, she tried to stretch out an arm through Basutoland to the sea.[249] Here even weak neighbors were effective to curtail the seaward growth of these inland states, because they were made the tools of one strong, rapacious neighbor. A central position teaches always the lesson of vigilance and preparedness for hostilities, as the Boer equipment in 1899, the military organization of Germany, and the bristling fortresses on the Swiss Alpine passes prove. [Sidenote: Mutual relations between center and periphery.]