Italy is unified, but under the pope (perhaps a bit of political manuevering by Pius IX before he swings towards conservativism). The "Italian Army" is the Order of Constantine the Great (making this group up), which has the three main vows (poverty, chastity, and obediance). They're allowed to marry, with wives and children (prior to their majority) performing rear-echelon support services. While officers join permanently, "enlisted" men may join for a period of at least four years. 20 years of good service by the enlisted men grants a hereditary noble title, that of Cavaliere Ereditario, thus qualifying their children to be officers.
While it functions as the Italian Army, it is open to all baptized male Catholics, and branches exist in several other nations. These branches will and do serve their host nations in just wars. Notably, during the First World War, Pope Benedict XV forbid the orders of all but Austria-Hungary to engage in combat (as only Austria-Hungary had a just war, German forfeiting that with their declaration of war on France and invasion of Belgium). The First World War ended when the Order invaded France (via Italy along with insurrection by the French branch) in response to the French refusal to accept the very generous peace terms by Kaiser Karl I of Austria-Hungary. As a result, France suffered painful reparations in its defeat by Germany and ceded historically Italian provinces (Savoy, Nice) to Italy.
Most of the soldiers in the Order function as highly trained infantry (all but the Austro-Hungarian branch being solely infantry), but the Italian and Austro-Hungarian branches do have several armored divisions.