The geographical position of a country also greatly influences the degree and character of its military preparation. It may be bordered on one or more sides by mountains and other obstacles calculated to diminish the probability of invasion; or the whole frontier may be wide open to an attack: the interior may be of such a nature as to furnish security to its own army, and yet be fatal to the enemy should he occupy it; or it may furnish him advantages far superior to his own country. It may be an island in the sea, and consequently exposed only to maritime descents--events of rare occurrence in modern times. Again, a nation may be placed between others who are interested in its security, their mutual jealousy preventing the molestation of the weaker neighbor. On the other hand, its political institutions may be such as to compel the others to unite in attacking it in order to secure themselves. The republics of Switzerland could remain unmolested in the midst of powerful monarchies; but revolutionary France brought upon herself the armies of all Europe. Climate has also some influence upon military character, but this influence is far less than that of education and discipline. Northern nations are said to be naturally more phlegmatic and sluggish than those of warmer climates; and yet the armies of Gustavus Adolphus, Charles XII., and Suwarrow, have shown themselves sufficiently active and impetuous, while the Greeks, Romans, and Spaniards, in the times of their glory, were patient, disciplined, and indefatigable, notwithstanding the reputed fickleness of ardent temperaments.