Alessandro Casati was not among those who professed themselves surprised by the outbreak of war at the end of July 1914, and he regarded Italy's military intervention in April 1915 as an inevitable if deplorable development. He participated in the fighting, ending the war with the rank of "Tenente colonnello" ("Lieutenant colonel"), having received the Bronze and Silver Medals of Military Valor ("...medagliere di bronzo e d'argento al valor militare"). He fought at the Battle of Asiago, led the successful attack by the 127th infantry regiment of the Florence Brigade at Monte Kobilek and was badly wounded at Bainsizza, following which he needed an operation. He also fought with his against the Austrians in the so-called in and around the Tonale Pass in the mountains north of Bergamo and Brescia. There are also a number of reports, albeit not formally confirmed, that during 1917 Alessandro Casati became a close associate of his fellow Lombard, General Capello, commander of the Second Army, providing critical advice and practical support, notably in respect of using innovative propaganda techniques to sustain troop morale, both before and after the important Battle of Caporetto. Capello was considered unusual in senior military circles because of the way he liked to surround himself with "intellectuals", and the "catholic liberal" Alessandro Casati was prominent among these.