After the Kingdom of Italy entered the war against the Austro-Hungarian Empire, on May 23 1915, from June 1915, following the occupation of Passo Brocón and Canal San Bovo and the advance into the Valley of Vanoi, the Italian side strengthened on the natural line shaped by the peaks and gaps of Forcella Valsorda – Cima Valsorda – Alpe Boalón – Pralongo – Cima di Mezzogiorno – Conte Moro – Col de la Crós – Forcella Regana.
Thanks to the favorable terrain shapes and also to the potentially powerful support that the artillery of Mount Totoga would have provided, the Pralongo passage provided excellent conditions for setting up a barrage in the valley floor, with the purpose of protecting the villages of Canal San Bovo and Caoria, occupied later on January 26 1916.
On the 18th of June 1916, the 32 Alpini of the Feltre Regiment set off on reconnaissance left the Pralongo passage. The 32 souls were all destined to fall into the ambush on the same day near the location of Refavaie.
The Italian operations of the summer of 1916 in the upper Vanoi, starting from the occupation of the summit of Cima Paradisi and the Fossernica ridges up to the bloody conquest of Mount Cauriòl, determined a radical change in the Italian front line which, at the end of autumn, ran along Mount Cauriol, the 2,454 “quota” of Gardinàl and 2,353 of the Busa Alta, the middle valley of Coldosè, Coltorondo and the 2,353 “quota” (Punta del Tabio) of Cima Cece; the trenches of Pralongo were therefore abandoned.
Following the battle of Caporetto, in the beginning of November 1917, the close of Pralongo witnessed in silence the folding of the columns of the retreating Alpini troops towards the new line on the Piave river. The trenches were used briefly by the 134th company of the Monrosa Brigade during the night of the 7th of November with the sole purpose of slowing down two Kaiserschützen companies.