The Trentino, somewhat detached from Aus tria, was connected with it by the Pusterthal and the Brenner Pass, by which two routes alone there is railway communication. Moun tain buttresses protected the Trentino salient, and an enemy attempting its conquest would have to advance mainly by the Adige Valley, only to be confronted by the strongly,fortified town of Trent, after overcoming which he would have to struggle through a wilderness of lateral valleys and subsequently force the main ridge of the chain at the Brenner Pass. Flank attacks on the containing wall 9f the Trentino were all but impossible, for Austria had converted it into an immense fortress bristling with guns. High up in the hills on the western side hes the Stelvio Pass, the highest carriage pass in the Alps, over 9,000 feet above sea-level. Here three frontiers meet among the clouds — Swiss, Italian and Austrian. Farther south, below the Ortler Massif, lies the Tonale Pass, offering no better passage for a large army. The frontier described the form of a huge horseshoe around nearly the northern half of Lake Garda and passed through the lake near its northern end. That little piece of the lake was in Austrian territory. Here the Italians quickly introduced a flotilla of gunboats and bot tled up the Austrians in their narrow end of the lake. This little ((squadron" patrolled the treach erous waters of Garda at all times and in all weathers, braving those sudden hurricanes — equal to anything an the open sea — for which the lake is notorious. Italian trenches and barri cades of barbed wirc ran from the Stelvio Pass down to the water's edge of the lake, continu ing on the opposite shore and eastern side of the salient, where conditions were still worse for invasion from the Italian side. The passes of the Dolomites offered no route northward to the Pusterthal. Thus the Austrian position in this sector consisted of a hollow headland of mountain jutting into the Italian plains be low, a barrier that was strengthened by the deep depression of Lake Garda, as it compelled an attack from the Italian plain to be made from distant bases east and west of the lake.
The next section of the Austro-Italian front—the Dolomite and Carnic ranges — formed a vast barrier of ramparts. Through • the main pass, Ampezzo, runs the great high road known as the Strada d'Alemagna (over 5,000 feet high) from Belluno to Toblach. In part it is a mere defile threatened by many dan ger points, while a number of passes farther eastward are mere bridle-paths, and there are none of military value to the southeast. On the Austrian side the Carnic Alps needed no fortifications, but at Tarvis there were military works to defend an approach from the Taglia-• mento to the Drave and to support (on the right) an Austrian concentration on the Isonzo. Tarvis was also an important point in the event of an Italian offensive against Vienna. Some old forts at the Predil Pass and Flitsch far ther south had been modernized by Austria, thus making the Isonzo a powerful defensive, position. Behind this the lines of the Save and Drave still remained to cover the approaches to, Gratz and Vienna. The third portion of the frontier was the low-lying ground between Cividale and Lake Marano, a narrow front barely 30 miles wide, protected from behind (on the Austrian side) by the Isonzo line and: some six miles of plain in front of Gorizia.
For many years the chief military interest of Italy was her northwestern frontier facing France, while the Austrian borderland was somewhat neglected. In late years, owing to improved relations with France, the situation changed and the centre of politico-strategic gravity shifted to the northeastern frontier.
where considerable work was carried out to prepare Italian troops and railroads for war on that side. Fortifications on a moderate • scale existed before the war; the road from Stelvio Pass was barred by the works at Borrnio, and from the Tonale Pass by others at Ponte di Legno, while Rocca d'Anfo guarded the exit from Giudicaria. The chief Italian frontier fortress in this theatre was Verona; other for tified zones of assembly had been prepared on the Adige and the Tagliamento. The Astico group of defenses, nearest Verona, extended from Arsiero to Asiago and connected with the worlcs of Val Logra and San Pietro on the frontier. Several forts lay scattered along the uppei Brenta and upper Piave, while farther east efforts had been devoted to the Tarvis line and the railroad from Osoppo to Pontebba. Thus the Italian covering troops on the fron tier had generally strong support behind them; assembly positions had been organized for both offensive and defensive operations; the left flank of Italian armies in Venetia had been made fairly secure; and finally, operations to-. ward the upper Adige and the Pusterthal had been facilitated.
The general idea originally was that the Italian armies might assemble behind the Brenta with their flanks resting on Venice and Verona, and that as they advanced eastward their left would be secured by troops and works in the upper valleys of the rivers. With these leading ideas the railway policy of Italy in general conformed. Of great importance, also, was the question of the seasons. The av erage Alpine pass is only free from snow for about five months in the year, and the mule-tracks over the highest coLs. (defiles) ior not more than three months. Before the French Revolution it was not the custom for armies to begin operations in the Alps before July, and usually those armies went into win ter quarters at the end of October. Later on, lower and more accessible sectors of the Alps were crossed between April and December, and the higher Alps betvveen May and November. It has been said that there is no prospect on earth quite like the immense irregular cres cent of serrated peak and towering mountain wall that is thrown around Italy on the north, as it unrolls itself from the plains of Lom bardy and Venetia. lit the teeth of the Aus trians — and a natuie. it were, as well — the Italians carried the line of entrenchments across wooded hills, meadows, torrents and snow-clad slopes. In many places the trenches had to be blasted out of the rock, and were re inforced with concrete or anything that mili tary science or nature could offer to render them invulnerable. The outstanding feature of the cainpaign when it opened was that the Ital ians were always going up while the Anstrians only needed to come down. The former were below, and the latter high above on that immense natural rampart of mountains. The possession of the Trentmo or Italian Tyrol was a matter of vital importance to Italy. The lcingdom was protected by the powerful mountain barrier against invasion from France and Switzerland. But by retaining the Trentino after withdraw ing from Italy in 1866, and by occupying the mountain passes down to the foot of the mountains as far as Lake Garda, Austna oc cupied with her army a wide breach in Italy's defense. The Austrians could thus easily in vade the country and strike at Verona, Padua and Venice by marching to the east, or at Bres cia. and Milan by turning to the west. The po sitions held by Austria in the Trentino, in Istria and in Dalmatia were largely inhabited by. Italians who suffered severely under Aus trian rule: the short-sighted policy of Austria had earned her the bitterest hatred of the Italians.