The Italians were the first to introduce the machine gun and this was during 1915 in the midst of World War 1 with their Villa-Perosa system. However, this weapon was hardly a suitable submachine gun design with its twin side-by-side barrel arrangement despite the system's overall portability and pistol caliber - seeing more use as a squad support solution or on aircraft as a mounted weapon. The first true submachine gun form came in the German Bergmann Model of 1918 (MP18) which saw some service before the end of the war.
Italian work on submachine guns continued throughout the interwar years leading up to World War 2 (1939-1945). When the war began in September of 1939, Italy formed with the Germans and became one of the major components of the Axis powers (becoming a more active part after May 1940). However, Italian participation as an Axis member ended with the Italian surrender in September of 1943. The tumultuous period that followed was the Italian Civil War (1943-1945) which pitted German-backed Italian Social Republic forces against an Italian resistance supported by the United States, Britain, and others.
Between 1944 and 1945, some 600 of a new Italian submachine gun were manufactured with Fabbrica Fratelli Giandoso as the "TZ-45". The weapon was designed by brothers Tono and Zorzoli Giandoso in 1944 and delivered to Socialist Italian forces. Other ventures of this time sought to outfit Socialist forces with similar tools - the Brescia FNAB-43 submachine gun being another example (7,000 produced).
The TZ-45 was chambered for the readily-available and proven 9x19mm Parabellum German pistol cartridge feeding from a 40-round detachable box magazine. The action relied on a blowback system with selective fire possible. Rate-of-fire reached 800 rounds-per-minute with muzzle velocity reaching 1,200 feet-per-second. Effective ranges were out to 500 feet - suitable for short- and medium-range encounters. Sighting was through a front/rear iron pairing.
Externally, the submachine gun took on a conventional arrangement with a pistol grip/trigger unit situated at the extreme rear of the metal body. A telescoping wire butt was fitted for support and portability. The receiver was mainly rounded in its shape with the barrel exposed along most of its length ahead. The magazine feed was under the receiver in the usual way though considerably ahead of the trigger area. The ejection port was cut into the top of the receiver, well ahead of the firer's face.
Due to its hasty design and production, the TZ-45 was not a well received automatic weapon system. Regardless, it was available and needed during the uprising of 1943-1945 and continued service until the end of the war. Some of the guns fell into the hands of the German Army and were used against any and all of its enemies into the final days. At the end of the war, the weapons were tested by the Allies (namely Britain and the United States) and found to be quite sub-par when compared to contemporaries. They were quickly discarded and deemed largely unreliable and poorly made weapons.
The end of the war did not end the story of the TZ-45 for its rights were sold off to the Burmese military where the weapons were serially manufactured under the local designation of "BA-42". The weapon's issues continued to plague it in service yet these guns were in use up until the early part of the 1990s - though by this time in second-line roles. Burmese production spanned from 1952 to 1955 adding another 5,400 of the guns to total production.