During World War I, when Italy declared war on Austria-Hungary on 23 May 1915, San Marino remained neutral and Italy adopted a hostile view of Sammarinese neutrality, suspecting that San Marino could harbour Austrian spies who could be given access to its new radiotelegraph station. Italy tried to forcibly establish a detachment of Carabinieri in the republic and then cut the republic's telephone lines when it did not comply. Two groups of ten volunteers joined Italian forces in the fighting on the Italian front, the first as combatants and the second as a medical corps operating a Red Cross field hospital. The existence of this hospital later caused Austria-Hungary to suspend diplomatic relations with San Marino.