The Italian advance towards Val Badia, Val Pusteria and Brennero was halted at the Valparola Pass in the face of the Austrian trenches.
Realising the futility of surface to surface attacks both armies began to excavate galleries and caverns in the mountain with the intent of blowing up their adversaries and fortifying their own positions.
Inside Lagazuoi today it is still possible to see the long tunnels, wooden huts, emplacements and trenches which form the open air museum of the Great War.
The trenches of the two opposing armies snaked their way along the summits of the mountains around Lagazuoi: Tofane, Castelletto, Great Lagazuoi, Sasso di Stria, Settsas , Col di Lana and Marmolada .
At the Cinque Torri (Five Towers) and Averau spread the second Italian line with artillery emplacements and floodlights to light up the mountain side of Lagazuoi.
It was soon clear to both sides that the best protection from enemy artillery fire was provided by the mountain itself and so began the excavations with emplacements and encampments transforming Piccolo Lagazuoi into a natural fortification.
To the Austrians, we owe the detailed plans of all the Lagazuoi galleries remained after the retreat of the Italian army in November 1917, following the defeat at Caporetto.
The illustration shows the location of the first 10 gallery systems on Piccolo Lagazuoi.
On 20th october 1915 an Alpini troop unit occupied the ledge halfway up the rock face of the Piccolo Lagazuoi, a wide rocky step which crosses the mountain halfway up and was surprisingly ignored by the Austrians.
The Martini Ledge, named after the name of the battalion commander who occupied it, soon became a thorn in the eye of the Austrians.
From there the Italians could hit scot-free the Vonbank emplacement with machine guns and grenades. Both armies began to dig the rock of the mountain, realizing shelters for the men and weapons they needed to survive and turning Mount Lagazuoi into a fortress of the 20th century.
They soon discovered that the only way to conquer the enemy's fortified emplacements was to dig a mine tunnel, to approach the enemy this way and blow him up. Five mines were blown up: four Austrian mines against the Martini Ledge and an Italian mine intended to conquer the pre-summit of Mount Lagazuoi.