The defences of the road over the Brenner, ever since the downfall of the Roman empire, had to be looked to most carefully, for the plain between the Mincio and the Adige, to the south of the Lake of Garda, is the least-protected part of Italy from a military point of view. History has proved this. Well might the peaceable inhabitants of the plain consecrate this Alpine road to the gods, and intrust its defence to the neighbouring tribes. But the northern barbarians were not to be stopped by altars; and many a time they swept down it like an avalanche, pillaging the towns and massacring the inhabitants. No spot on the earth’s surface has been so frequently saturated with human blood. Most of the battles for the possession of Italy, down to our own days, were fought near the mouth of the upper valley of the Adige. Hardly a town or a village of this small district but {223} has gained a mournful notoriety in the dark pages of human history. It is there we must seek for the battle-fields of Castiglione, Lonato, Rivoli, Solferino, and Custozza. When the Austrians held Lombardy and Venice, they took care to protect this district by the four fortresses known as the Quadrilateral (Verona, Peschiera, Mantua, and Legnago) and other works. These constituted the “key of the house,” of which Italy has now repossessed herself. [Illustration: Fig. 74.—MOUTH OF THE ADIGE VALLEY. From the Austrian Staff Map. Scale 1 : 397,000.] The configuration of the country which rendered these defiles of the Alps of importance strategically, likewise insured their commercial importance. The fortresses were placed there to defend the passes, the commercial entrepôts to intercept the trade. The rank of these places of commerce depends essentially upon the number and the importance of the roads which converge upon them. Turin, upon which converge all the Alpine roads from Mont Blanc to the Apennines, naturally became one of the vital points of European commerce. Milan, to which lead the seven great Alpine routes of the Simplon, the Gotthard, the Bernardino, the Splügen, the Julier, the Maloya, and the Stelvio, was marked out by nature as a commercial emporium. Bologna, too, which was separated by the swamps of the Po from the Alpine passes, has risen into importance since railways have joined it to Vienna, Paris, Marseilles, and Naples. {224}