There were limitations placed upon both the size, deployment, and structures of the Italian military in the 1947 Peace Treaty- Warning PDF. Part IV of the Treaty demanded that Italy defortify its frontiers with France and Yugoslavia and deploy no weapons that could reach into these areas. Italian islands like Pantellaria had to be completely demilitarized. Both the Italian Air Force and the Army were limited to two hundred planes and tanks. Furthermore, the Army was limited to 250,000 men and the Navy could not acquire new ships until after 1950 and then could not build heavy units like battleships or aircraft carriers. The Allies also forbid Italy from developing either nuclear or guided missile technology.
Italy's joining of NATO two years later and the formation of the European Defense Community (EDC) in 1950 rendered many of these provisions and limitations moot. Although the EDC foundered amongst much wrangling and apprehension, the initial treaty allowed Italy to release itself from the military provisions of the 1947 Treaty. Since Italian rearmament took place under the auspices of these two institutions, there was little opposition among Western European and American governments over this development. The Italians allowed for the US deployment of IRBMs and the Italian Navy launched two large guided-missile cruisers and flirted with an abortive plan to deploy Polaris missiles on its ships.
The rearmament and incorporation of Italian troops into the defense structures of Western Europe were congruent with the wider trend of rearming former Axis powers. In both the cases of Japan and West Germany, the embryo of a postwar military emerged in the form of police forces that maintained domestic order and patrolled the borders. These polices forces often had a strong paramilitary character and were staffed by veterans from the war. Treaties with the US and Western forces in the 1950s allowed for these policing institutions to be expanded into proper military formations, albeit often with explicit provisions that they would be both subordinate to civilian control and be incorporated into defense organizations which were dominated by US military leaders for most of the Cold War. In the case of Japan, its armed forces, called the Self-Defense Forces, developed very strong defensive capabilities but lacked many offensive weapons that would allow it to project this military power outside of the home islands or immediate environs without major US assistance. The Japanese constitution explicitly outlawed war and renounced offensive weapons which resulted in stretching the terminology for military equipment (just recently, the Maritime Self-Defense Forces just launched a "destroyer" which really looks like an aircraft carrier). These often self-imposed restrictions caused a degree of friction with the US in the latter half of the Cold War. Kissinger, for example, resented how the Japanese would never really step away from their defensive orientation and help the over-stretched US forces during the tail-end of the Vietnam War and its aftermath. This criticism avowed civilian control over the Japanese and German armed forces have often created the mistaken impression that neither Japan nor the FRG possessed a military worth much value. In fact, both forces were highly advanced, relatively large, and well-trained and their existence (and staffing by officers from the Second World War) was a consistent source of criticism within Soviet propaganda during the Cold War.
Sources
Di Nolfo, Ennio. Power in Europe? II: Great Britain, France, Germany, and Italy, and the Origins of the EEC, 1952-1957. Berlin: W. de Gruyter, 1992.
Hattendorf, John B. Naval Policy and Strategy in the Mediterranean: Past, Present, and Future. London: Frank Cass, 2000.