Slavs were present in the region since the 7th century. Montenegro got its name during the rule of the Crnojević which was one of the first Montenegrin royal houses. Since the violent Christmas Uprising (1919), which saw fighting between the pro-Petrovic guerillas and the Karadjordjevic troops, there was a significant opposition to unification with Serbia although majority of Montenegrin people were pro unification. Following the end of the World War II the population was shifted overwhelmingly in favour of separate Montenegrin ethnicity (91%) due to Montenegrin self awareness. Following the collapse of Communism in Yugoslavia however, some Montenegrins began to self-identify as Serbs again (31,99%), while the largest proportion of citizens of Montenegro still preserved their Montenegrin self-identification (43,16%)- Christians and Muslims all together. This has deepened further since the movement for full Montenegrin independence from the Federal Republic of Yugoslavia began to gain ground in 1991, and ultimately narrowly succeeded in the referendum of May 2006 (having been rejected in 1992). The Montenegro Serbs do not consider themselves separate from the Montenegrin nation but instead believe that all genuine slavic Montenegrins are Serbs by ethnicity, and that Montenegrin nation is one fraction of "Serbdom".
In the 2011 census, around 280,000 or 44,98% of the population of Montenegro identified themselves as ethnic Montenegrins, while around 180,000 or 28,73% identified themselves as Serbs. The number of "Montenegrins", "Serbs" and "Bosniaks" fluctuates wildly from census to census, not due to real changes in the populace, but due to changes in how people experience their identity. According to the 2002 census, there are around 70,000 ethnic Montenegrins in Serbia, accounting for 0.92% of the Republic's population. The number of Montenegrin citizens in Serbia runs to several hundreds of thousands (nearly 300,000 est.), but most of them identify as Serbs. In addition, a significant number of Serbs in Serbia and Bosnia-Herzegovina are of Montenegrin ancestry, but exact numbers are difficult to assess – the inhabitants of Montenegro contributed greatly to the repopulation of a depopulated Serbia after two rebellions against the Ottoman Empire in the early 19th century, with a half of the population of Sumadija and the surroundings being populated by people originally from Montenegro, and several prominent individuals of the Serbian 19th & early 20th century intelligentsia and entrepreneurs being descendents of people originally from Montenegro.
On 19 October 2007, a new Constitution was adopted that proclaimed the Montenegrin language official, and attributed Montenegrin statehood and sovereignty to all citizens of Montenegro