Pannonia

Pannonia was an ancient Balkan province of the Roman Empire bounded north and east by the Danube, coterminous westward with Noricum and upper Italy, and southward with Dalmatia and upper Moesia. Pannonia was located over the territory of the present-day western Hungary, eastern Austria, northern Croatia, north-western Serbia, Slovenia, western Slovakia and northern Bosnia and Herzegovina.

Pannonia in "Give Me Back My Legions!"
Due to the fact that Tiberius was busy putting down a rebellion in Pannonia, the Roman Emperor Augustus was unable to send his most trusted general to pacify the region of Germania and bring it fully into the Roman Empire.

Instead, he had to send the inexperienced Publius Varus to do the job. Varus failed in a spectacular fashion.