The Illyrian movement (; ) was a pan-South-Slavic cultural and political campaign with roots in the early modern period, and revived by a group of young Croatian intellectuals during the first half of the 19th century, around the years of 1835 to 1863.Despalatović, Elinor Murray. Ljudevit Gaj and the Illyrian Movement. Boulder: East European Quarterly, 1975. This movement aimed to create a Croatian national establishment in Austria-Hungary through linguistic and ethnic unity, and through it lay the foundation for cultural and linguistic unification of all South Slavs under the revived umbrella term Illyrian.

Aspects of the movement pertaining to the development of Croatian culture are considered in Croatian historiography to be part of the Croatian national revival ().

Name Views of Josip Kušević inspired the nascent Croatian national revival movement. His view that the South Slavs are indigenous population, tracing their origin to the Illyrians inhabiting the Balkan Peninsula in ancient times, led him to hypothesise that there is a common South Slavic language which he referred to as the idioma Croatico-Slavico-Illyricum (Croatian-Slavic-Illyrian language). In the 19th century, the name Illyrian was chosen by the members of the movement as a reference to the theory according to which South Slavs descend from ancient Illyrians. Fearing provincial particularism, reformers believed that the Illyrian name would make it easier to implement literary unity. The name Illyrian (Slavic) had already been used in reference to the South Slavic dialects spoken there at the time.

Historical context In 19th-century Europe, liberalism and nationalism were ideologies which came to the forefront of political culture. In Central Europe, where the Habsburg Empire had long asserted control over a variety of ethnic and cultural groups, nationalism appeared in a standard format. The beginning of the 19th century "was the period when the smaller, mostly Slavic nationalities of the empire – Czechs, Slovaks, Slovenes, Croats, and Serbs – remembered their historical traditions, revived their native languages as literary languages, reappropriated their traditions and folklore, in short reasserted their existence as nations."Sperber, Jonathan. The European Revolutions, 1848–1851. New York: Cambridge University Press, 2005. page 99. This revival of national heritage encompasses the Illyrian Movement in Croatia.

In 1813, the bishop of Zagreb, Maksimilijan Vrhovac, issued a plea for the collection of "national treasures" (), thereby heralding the national revival movement. Influenced by his father Josip, who was the first mayor in French-controlled Karlovac and one of its first Freemasons, Juraj Šporer attempted to publish the first newspaper in the 'home-born' () language. His project was aborted because of the complete lack of interest for a newspaper published in his native language.

Just as Croatia felt nationalistic stirrings at this time, so did its larger neighbors, Hungary and Austria. Croats were uneasy with rising Hungarian nationalism, which pursued reduction of the Croatian autonomy and increased Magyarization. In order to preserve their autonomy, Croats pursued a deepening of their culture and a revival of their heritage. Members of the Illyrian movement were heavily influenced by the 1700 publication Croatia Rediviva.Šišić, Hrvatska Historiografija pp. 46

In the beginning of the 1830s, a group of young Croatian writers initially led by Ljudevit Gaj gathered in Zagreb and established a movement for national renewal and unity of all South Slavs within the Habsburg Monarchy. The city of Zagreb had become an important center of political, economic, and cultural activity, so it was the center of the movement. Count Janko Drašković published his Dissertation in 1832, a pamphlet that later came to be considered the political, economic, social and cultural program of the movement, as it promoted the native language as official, more autonomy from central government, and better education and enlightenment for the common people. Gaj served as the leader of the movement as a whole in the beginning for eight or nine years, at which point the leadership changed hands.Despalatović, Elinor Murray. Ljudevit Gaj and the Illyrian Movement. Boulder: East European Quarterly, 1975.

The greatest issue for Illyrians was the establishment of a standard language as a counter-weight to Hungarian, and the promotion of Croatian written literature and official culture. Illyrians envisioned a single literary language and orthography to serve as a means of cultural and national unification, paving the way for a general national revival.

Illyrian language conceptions In 1830, Ljudevit Gaj published ("Brief basics of the Croatian-Slavic orthography"), which was the first linguistic work to be published during the movement. In it he presented his proposal for a reform of the Illyrian alphabet, which included the introduction of diacritics. This was motivated by the alphabets of other Slavic peoples who wrote in the Latin script (Czechs, Slovaks and Poles), as well as by earlier domestic practices such as the alphabet used by Pavao Ritter Vitezović. After Vitezović's letters l̃ and ñ, Gaj introduced tilde as a diacritic in the letters c̃, z̃, s̃, l̃, ñ, d̃ and g̃. However, for tactical reasons that notation has not been thoroughly applied. Even though the alphabetic reform was originally intended for the speakers of the Kajkavian () dialect, in his work Gaj put forward the idea of a common alphabet for all South Slavs using Latin script, which would lay the foundation for the common literary language.

In 1835, Gaj started publishing ("Croatian newspapers") and in Kajkavian and using old Kajkavian alphabet. But since the very beginning Gaj's magazines also contained pieces from older Shtokavian dialect () literature, namely Ragusan, to pave the way for the introduction of a common literary language on Shtokavian basis. The tenth issue of his is already using the new alphabet and Shtokavian in some of the published pieces, and since the 29th issue the new alphabet is dominant.

On 5 December 1835, Gaj published a Proclamation announcing the publication of ("Illyrian folk newspapers") and , abandoning old alphabet and introducing the Shtokavian dialect. The terminological shift from "Croatian" to "Illyrian" more accurately reflected the ideological goals of the Illyrian movement, as well as the usage of the Shtokavian dialect which was at that period the most widely spoken dialect. Illyrians' goal was to make that language more accessible to the Kajkavian and Chakavian () speakers. In that spirit, Gaj's 1835 Proclamation states:

Beside the fundamental Illyirian ethnological notion of South Slavs as the descendants of ancient Illyrians, awareness of national distinctiveness was also present. Thus Gaj writes in 1839 in : "Our intention is not to abolish individual names, but unify them under a general name, because each of the individual names carries its own individual history, which gathered together comprise a more general history of the Illyrian nation."In original: Naměra naša nije posebna imena ukinuti, nego ih samo pod skupnim imenom sjediniti, jer su sa svakim posebnim imenom skopčani posebni događaji koji skupljeni čine dogodovštinu obćenite narodnosti ilirske. In an attempt to overcome regional fragmentation and achieve unification, followers of the movement promote Illyrian name, making concessions in language and orthography. Drawing on existing literary traditions in three different dialects, and in an attempt to ease the linguistic and cultural unification, Illyrians advocate the usage of some archaic forms in grammar, and some Kajkavian and Chakavian words. Such changes were hoped to be acceptable to everyone using the Illyrian language.

Orthography and alphabet Acting on the intention of Illyrians to create a common literary language and orthography for all South Slavs, Gaj in his 1835 article abandoned his original alphabet. Of the many letters with diacritics he initially proposed, only č, ž, š and ě were retained,ě was used to mark any of the possible reflexes of the Proto-Slavic yat sound. and due to printing difficulties carons were used instead of tildes. The digraphs lj́, nj́, dj́ and dž were used instead of the former l̃, ñ, d̃ and g̃, as these digraphs were already known from the Slavonian alphabet, which was the most widespread alphabet before the Illyrian movement. What today is written as ć was written as both ć and tj́, while the letter j́ was soon to be replaced by j. This alphabet system introduced by Gaj was used until the late 19th century, when Đuro Daničić finally introduced the letter đ for dj, and generalized the usage of ć, yielding the modern Croatian alphabet.

With respect to orthographic issues, the Illyrians endorsed the so-called etymological (also called morphonological) orthography, spelling words according to their morphology and etymology. This was opposed to the contemporaneous phonological orthography "write as you speak, and speak as you write"In original: Piši kao što govoriš, a čitaj kako je napisano! advocated by Vuk Stefanović Karadžić and his followers. The Illyrians justified their spellings as being more comprehensible and easier to learn, while also better reflecting the orthographic practices of other Slavic peoples. They pitted Karadžić's adage against their own: "speak for the ears, write for the eyes".In original: Govori za uši, a piši za oči!

Language characteristics Gaj's main associates and followers were Vjekoslav Babukić and Antun Mažuranić. In their linguistic manuals (Babukić's 1836 , "The basics of Slavic grammar of the Illyrian dialect"; extended edition as 1854 , "Illyrian grammar"; Mažuranić's 1839 , "The foundation of the Illyrian and Latin language") they were led by the ideological goals of the Illyrian movement, building upon the language supported by the movement's adherents, and which was later advocated by the so-called Zagreb Philological School.

Two of the most important grammatical traits advocated by Illyrians were old inflectional endings for the dative, locative and instrumental plural of nouns, as well as the ending -ah in genitive plural of nouns, which earned them a derisive nickname "Ahavians" (). For example: genitive plural: , , , , , dative plural: , , , , , locative plural: , , , , , instrumental plural: , , , , ,

A different set of issues were involved in writing reflexes of the Proto-Slavic yat sound, as well as the syllabic /r/. All of the possible yat reflexes (i, e, je or ije, depending on the dialect) were covered by the letter ě, which was derisively called "horned e" (). Initially it was suggested that everyone reads ě according to their local pronunciation, though it would be preferable to publicly pronounce it as [je] or [ije]Babukić 1836: "u čitanju priučavati se ilirski ě razložno kao je izgovarati"Mažuranić 1839: "u čitanju i u školah ... kano ié ili je izgovarati ga" For syllabic /r/ they were convinced that the pronunciation differs from non-syllabic /r/, so they introduced spelling of the accompanying vowel as well (àr, èr: e.g. , ).

Impact As opposed to the alphabet which is in a slightly modified form used to this day for Croatian, grammatical and orthographic practices advocated by Illyrians provoked resentment and opposition by some contemporaries as well as by future generations of linguists. Illyrians were criticized from different points of view, and their practices were attacked more often individually rather than as a system, and had a different lifespan, eventually suffering the same fate: disappearance from the language. The so-called etymological orthography survived the longest, until the turn of the century.

Cultural development