Christianity was adopted by the Serbian rulers in ca.
870, and by the mid-10th-century the Serbian state stretched the Adriatic Sea by the Neretva, the Sava, the Morava, and Skadar.
The Romans conquered much of the territory in the 2nd century BC.
In 167 BC the Roman province of Illyricum was established; the remainder was conquered around 75 BC, forming the Roman province of Moesia Superior; the modern-day Srem region was conquered in 9 BC; and Bačka and Banat in 106 AD after the Dacian Wars.
Three Habsburg invasions and numerous rebellions constantly challenged Ottoman rule.
Archeological evidence of Paleolithic settlements on the territory of present-day Serbia are scarce.
Following disastrous casualties in World War I, and the subsequent unification of the former Habsburg crownland of Vojvodina (and other territories) with Serbia, the country co-founded Yugoslavia with other South Slavic peoples, which would exist in various political formations until the Yugoslav Wars of the 1990s.
During the breakup of Yugoslavia, Serbia formed a union with Montenegro, which dissolved peacefully in 2006.
A fragment of a human jaw, was found in Sićevo (Mala Balanica) and believed to be up to 525,000—397,000 years old.
Approximately around 6,500 years BC, during the Neolithic, the Starčevo, and Vinča cultures existed in or near modern-day Belgrade and dominated much of the Southeastern Europe, (as well as parts of Central Europe and Asia Minor).