The strategic plan of the Italian generals was determined by hard geographical facts. The Italo-Austrian frontier is about 480 miles long, divided naturally into three sections. On the west the Austrian province of Trentino indents Italian territory like a wedge; next comes the great wall of the Dolomites and the Carnic and Julian Alps; then, on the east, a boundary line running north and south between the main Alpine chain and the Adriatic Sea. Steep mountain heights dominated by Austrian troops guarded the first two parts of this frontier. Only on the eastern border, from Pontebba to the Adriatic was Italian offensive on a large scale at all feasible; but before offensive operations could be started here it was necessary for the Italians to close the open gates to the north. Here in the north lay Italy's problem at the opening of the war; and here her armies confronted an almost impossible task. In a word, they had to fight uphill. A salient, such as that formed by the Trentino, may offer dangers for the side that holds it--an example of which is the Russian position in Poland at the opening of the war; but the Trentino situation was quite unlike that in Poland. The sides of the Trentino were buttressed with mountains. The most tempting avenue of invasion was the valley of the Adige River. An enemy advancing by this route would find himself confronted with the strongly fortified town of Trent, which long resisted attacks from Venice in the Middle Ages. Having forced his way past Trent the enemy would be in a wilderness of lateral valleys with the main ridge of the Alpine chain, at the Brenner, still before him. On the western side of the Trentino is the lofty Stelvio Pass, leading from the Upper Adige to the valley of Adda. This pass is 9,000 feet high and its narrow defiles were easily defended. To the south lies the pass of Tonale over which runs the road from Noce to the Oglio, but this offers similar difficulties. The road pass of Cornelle, close to Lake Garda, is too narrow for any considerable force. On the eastern side of the salient conditions for invasion are still worse. The railway from Venice to Innsbruck crosses the Valsugana at Tezze, but the Brenta valley through which it runs is a difficult road to Trent. Summed up, the salient of the Trentino was an ideal position for those who held it, both offensive and defensive. The few breaches by which invasion could come were a source of strength rather than weakness, because they compelled attack from the Italian plain to be made on divergent lines from different bases.