In the meantime tens of kilometres further to the north of Mount San Michele, preparations for new devastating action on the Belluno Dolomites were under way. A year after the start of the conflict the valley of Falzarego remained blocked and the army was divided, following two different directions: a section concentrated on Col di Lana (where a mine had been exploded in April 1916) while the other section penetrated into the north at Val Travenanzes, a wild valley, completely uninhabited and lacking any infrastructure and surrounded by the massive Tofane Mountains.
After the peak of Tofana di Rozes was occupied without any skirmish, the Italians had to liberate a second hill, the Castelletto, from the Austro-Hungarian troops. But the action immediately appeared very difficult: the Habsburg army had excavated many tunnels and caverns that the Italian artillery was unable to reach from its positions.
For this reason at the end of 1915 two Italian sappers began to devise a plan to explode the top of the Castelletto by means of an internal tunnel that would link Tofana di Rozes to the Austrian encampment some 500 metres away. According to their calculations, 35 tons of gelignite were necessary; this was a powerful explosive consisting of nitroglycerine and potassium nitrate. Works started in winter and by June 1916 the Italian soldiers had reached up to only a few metres away from the peak, just underneath the positions of the Austro-Hungarian troops.
Hans Schneeberger, the officer of the Käiserjager at Castelletto, knew what was happening underneath him but proudly did not abandon his position. The simultaneous counter offensive on the Asiago plateau and on the Russian front did not allow him to ask for reinforcements and he awaited his destiny with indifference.
At the start of July the sound of the drilling ceased and a heavy Italian bombardment preceded the start of the operation. At 3.30 am on 11th July the mine with 35 tons of explosives was activated and a gigantic cloud of smoke, dust and debris rose in the sky above the Italian front. The explosives had done their work but the initiative by the Italians failed: Schneeberger and ten other soldiers remained alive and succeeded in repelling the attack by a number of Italian men who killed themselves when they entered the crater that was full of carbon monoxide that had been created by the explosion of the mine. The Austrians retreated 500 metres downstream and set up a new defensive line. The pass therefore remained blocked and a new Italian plan, somewhat unrealistic, to dig a tunnel some two kilometres long under the Falzarego pass to outflank the Austro-Hungarian defences was interrupted by the retreat of Caporetto.
