alley 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.

The second part of the frontier is the ramparts of the Dolomite and
Carnic ranges through which an important offensive was possible for
neither belligerent. The main pass, at Ampezzo, 5,000 feet high, makes
a sharp detour toward the west to circumvent the mass of Cristallo,
and here the road is a narrow defile commanded by a hundred points of
danger. The adjacent passes of Misurina and the Monte Croce are no
better, and the defiles to the east contain little more than bridle
paths. The lowest pass, which leads from the valley of the Fella by
Pontebba to the upper streams of the Drave and carries the railway
from Venice to Vienna is only 2,615 feet high at its greatest
elevation. Although this is the easiest of the great routes through
the mountain barrier, it is still narrow and difficult. A modern army
given the advantages of time and preparation should be able to close
and hold it with ease.

Although the maps show few natural difficulties on the third section
of the frontier to compare with those farther west, it is not the
obvious avenue of attack a hasty survey would seem to suggest. It is
only twenty miles wide and behind it is the line of the R