In 1919, at the time of its annexation, the middle part of the County of Tyrol which is today called South Tyrol (in Italian Alto Adige) was inhabited by almost 90% German speakers.  Under the 1939 South Tyrol Option Agreement, Adolf Hitler and Benito Mussolini determined the status of the German and Ladin (Rhaeto-Romanic) ethnic groups living in the region. They could emigrate to Germany, or stay in Italy and accept their complete Italianization. As a consequence of this, the society of South Tyrol was deeply riven. Those who wanted to stay, the so-called Dableiber, were condemned as traitors while those who left (Optanten) were defamed as Nazis. Because of the outbreak of World War II, this agreement was never fully implemented. Illegal Katakombenschulen ("Catacomb schools") were set up to teach children the German language.
In 1923, three years after South Tyrol had been formally annexed, Italian place names, almost entirely based on the Prontuario dei nomi locali dell'Alto Adige , were made official by means of a decree.  The German name "Tyrol" was banned, likewise its derivants and compound words such as "Tyrolean" and "South Tyrolean".  German newspapers, publishing houses, organized clubs and associations, including the South Tyrolean Alpine Club had to be renamed, with the decree said to have been strictly enforced by Italian carabinieri on the ground.  The basis for these actions was a manifesto published by Ettore Tolomei on 15 July 1923, called the Provvedimenti per l'Alto Adige ("Measures for the Alto Adige"), becoming the blueprint for the Italianization campaign.  Its 32 measures were: 
In October 1923, the "use of the Italian language became mandatory on all levels of federal, provincial and local government".  Regulations by the fascist authorities required that all kinds of signs and public notices had to be in Italian only, while maps, postcards and other graphic material had to show Italian place names.  In September 1925, Italian became the sole permissible language in courts of law, meaning that, from then on, cases could be heard only in Italian.  The fascist law regulations remained in effect after World War II, becoming a bone of contention for decades until they were eventually reconsidered in the 1990s. 
The German-language press, which was still published, was harassed by the authorities and subjected to censorship prior to publication.  In 1926 the fascist authorities began to publish their own German-language newspaper, the Alpenzeitung.  Other German-language papers were obliged to follow a strictly pro-regime editorial policy. 
The programme of Italianization was particularly forcefully applied in schools, aiming at the destruction of the German school system.  As of 1928, Italian had become the only language of instruction in 760 South Tyrolean classes, affecting over 360 schools and 30,000 pupils.  Likewise, German Kindergarten were required to use Italian, while substitutes were forced to shut down.  German teachers were systematically dismissed on the grounds of "insufficient didactics", or transferred to the south, from where Italian teachers were recruited instead.  Degrees from Austrian or German universities became valid only through an additional stay of one year at an Italian university. 
In religious affairs, a royal decree of November 1923 required religious instruction in Italian for all Italianized schools.  Fascist calls for the Italianization of German charitable organizations, religious orders and the complete abolition of German religious instruction to the Vatican were not entirely successful, not in the least due to the repeated interventions of the Bishop of Brixen and the setting up of informal Parish schools.  In state schools, though, Italian became mandatory for the last five classes, while the use of German was only allowed in teaching the Italian catechism in the first three years. 
The German-speaking population reacted by the establishment of Katakombenschulen ("catacomb schools"), clandestine home schools outside the Italianized standard educational system.  German schoolbooks were secretly smuggled across the border, often hidden in religious buildings before being distributed to the South Tyroleans pupils.  After initial difficulties, secret seminars for the instruction of teachers were organized throughout the province, usually under the protection of the Catholic church.  Fascist countermeasures ranged from searches and confiscations to imprisonments and deportations.  The balancing act between the instruction in Italian and German schools, where often the exact opposite was taught, especially in history and the social fields, is said to have left many Tyrolean pupils with a torn identity.  The newly composed Bozner Bergsteigerlied quickly became one of South Tyrol's unofficial hymns by celebrating an unbroken attachment of the South Tyroleans to their homeland. In the 21st century, just over 100 years after the Italian annexation of the region,  64% of the population of South Tyrol speak German as their first and everyday language.
After the end of the Second World War, reform processes tolerated the dual use of names on street signs, while the Italian names remain as the official ones, based on the 1940 law.
In the 1990s, a commission consisting of the Professors Josef Breu (Vienna, representing Austria in the Toponymy commission of the UN), Peter Glatthard (Berne) and Carlo Alberto Mastrelli (Florence, current "Archivio per l'Alto Adige") failed as Mastrelli insisted on the fascist decrees, while Breu and Glatthard promoted the UN-Guidelines. 
South Tyrol, officially the Autonomous Province of Bolzano, is an autonomous province in Northern Italy, one of the two that make up the autonomous region of Trentino-Alto Adige/Südtirol. The province is the northernmost of Italy, the second largest, with an area of 7,400 square kilometres (2,857 sq mi) and has a total population of about 534,000 inhabitants as of 2021. Its capital and largest city is Bolzano.
Trentino-Alto Adige/Südtirol is an autonomous region of Italy, located in the northern part of the country. The region has a population of 1.1 million, of whom 62% speak Italian as their mother tongue, 30% speak South Tyrolean German and several foreign languages are spoken by immigrant communities. Since the 1970s, most legislative and administrative powers have been transferred to the two self-governing provinces that make up the region: the Province of Trento, commonly known as Trentino, and the Province of Bolzano, commonly known as South Tyrol. In South Tyrol, German remains the sizeable majority language.
Brixen is a town in South Tyrol, northern Italy, located about 40 kilometres (25 mi) north of Bolzano.
The South Tyrol Option Agreement was an agreement in effect between 1939 and 1943, when the native German and Ladin-speaking people in South Tyrol and several other municipalities of northern Italy were given the option of either emigrating to neighboring Nazi Germany or remaining in Fascist Italy, where the German minority was subjected to repressive Italianization efforts.
The Prontuario dei nomi locali dell'Alto Adige is a list of Italianized toponyms for mostly German place names in South Tyrol which was published in 1916 by the Royal Italian Geographic Society. The list was called the Prontuario in short and later formed an important part of the Italianization campaign initiated by the fascist regime, as it became the basis for the official place and district names in the Italian-annexed southern part of the County of Tyrol.
Katakombenschulen were clandestine schools established in Italian South Tyrol during the 1920s period of Fascist Italianization.
Modern-day South Tyrol, an autonomous Italian province created in 1948, was part of the Austro-Hungarian County of Tyrol until 1918. It was annexed by Italy following the defeat of the Central Powers in World War I. It has been part of a cross-border joint entity, the Euroregion Tyrol-South Tyrol-Trentino, since 2001.
The (Princely) County of Tyrol was an estate of the Holy Roman Empire established about 1140. After 1253, it was ruled by the House of Gorizia and from 1363 by the House of Habsburg. In 1804, the County of Tyrol, unified with the secularised prince-bishoprics of Trent and Brixen, became a crown land of the Austrian Empire. From 1867, it was a Cisleithanian crown land of Austria-Hungary.
Montan is a municipality with 1,701 inhabitants in the South of South Tyrol in northern Italy, about 15 km south of Bolzano. The name Montan comes from the Latin mons ("mountain").
Ettore Tolomei was an Italian nationalist and fascist. He was designated a Member of the Italian Senate in 1923, and ennobled as Conte della Vetta in 1937.
The Social Democratic Party of South Tyrol was a regionalist social-democratic and Christian-social party of German speakers in South Tyrol, Italy, that was active from 1972 to 1983.
The South Tyrolean Liberation Committee was an underground secessionist and terrorist organisation founded by Sepp Kerschbaumer and several combatants including Georg Klotz in the mid-1950s which aimed to achieve the right for self-determination for South Tyrol and the related secession from Italy via bomb attacks.
The Bozner Bergsteigerlied is one of the two unofficial hymns of the South Tyroleans, the other being the Andreas-Hofer-Lied. Its lyrics were composed in 1926 by Karl Felderer in Moos am Ritten to the melody of an old Tyrolean craftsmen's song.
Bolzano/Bozen railway station is the main station of Bolzano/Bozen, capital of the autonomous province of Alto Adige/Südtirol, in northeastern Italy.
South Tyrol is an autonomous province located in north-east Italy producing wine. This Austro-Italian wine region is noted for the distinct Austrian influences on the wine industry due to the region's long history under the rule of Austria-Hungary and Holy Roman Empires.
The South Tyrolean Unterland or Bozen Unterland is a section of the Etschtal valley stretching from the regional capital Bolzano (Bozen) down the Adige (Etsch) river to Tramin and Salorno (Salurn). The area is known for its history, particularly regarding Rhaetic, Roman, and Germanic archaeological sites; its bilingualism, and its viticulture; the Gewürztraminer grape originated here.
The politics of South Tyrol is conducted through a parliamentary, democratic autonomous province with a multi-party system. Executive power is exercised collectively by the Landesregierung, which is led by the Governor, referred to as "Landeshauptmann" in German. Legislative power is vested in the Landtag primarily, and secondarily on the provincial government. The judiciary is independent of the executive and the legislative branches. South Tyrol has been an autonomous province within the Italian Republic since 1948, when the Gruber – De Gasperi Agreement was agreed upon between Austria and Italy.
The South Tyrolean independence movement is a political movement in the Italian autonomous province of South Tyrol that calls for the secession of the region from Italy and its reunification with the State of Tyrol, Austria. Concurrently, some groups favor the establishment of an interim Free State of South Tyrol as a sovereign nation while reintegration is organized.
South Tyrolean German or Tyrolese is a dialect spoken in the northern Italian province of South Tyrol. It is generally considered to be a local variant of Southern Bavarian, and has many similarities with other South German languages such as Austrian German. The difference between other Bavarian and South Tyrolean is the influence of Italian and Ladin in its lexicon.
The following is a timeline of the history of the city of Bolzano/Bozen in the Trentino-South Tyrol region of Italy.
Media related to Italianization of South Tyrol at Wikimedia Commons