This paper discusses the historical development of the Croatian language in the second half of the 20th century, especially during the Socialist Federal Republic of Yugoslavia. The first part covers the period of the first half of the 20th century and the development of the Croatian language within the multinational community, monarchist Yugoslavia and the Kingdom of Serbs, Croats and Slovenes. The area of language, during the first Yugoslavia, was marked by strong linguistic violence that continued in the second Yugoslavia, founded in 1945. This paper presents the efforts of the Yugoslav unitarists to use Croatian language as a powerful weapon for the purpose of diminishing the value of a nation and to fight against national and linguistic autonomy. Novi Sad Agreement has been especially analyzed, as a symbol of the greater-serbian language policy, as well as the Declaration on the name and position of the Croatian language, as a symbol of resistance to linguistic violence. Also, the paper analyzes the importance of sociolinguistic factors in differentiating the two languages and the harmful effects of political institutions on the independent development of language.