Barbarians and Rome's legions battled along the Danube for 400 years

The Danube created a natural border, and the rulers of Rome, starting with the first emperor, Augustus, used it to mark the place where Rome ended and the frontier began.On one side of the river dwelled Romans, on the other were barbarians. Roman writers did not differentiate among the Germanic tribes who lived north of the Danube. (Discover Tacitus's account of the rebel queen who challeneged the Roman Empire.)The Germanic tribes that lived along the Danube were not monolithic. A papyrus found in Egypt reveals activities carried out by soldiers in one auxiliary unit on the Danube in the early second century A.D. Some were engaged as bodyguards to imperial officials, two groups traveled to Gaul to procure clothes and cereals, while three others went north of the Danube—one to supervise crops, one to do reconnaissance, and another on an unspecified expedition.For recruits who began their service on the Danube frontier, action was probably limited to the odd bandit attack or isolated barbarian incursion across the river for most of the first century A.D. But those who served in A.D. 85 would face the first of three Roman wars against the kingdom of Dacia (in what is Romania today), the strongest kingdom north of the Danube.The Dacians had no written language, so much of what is known about them comes from the archaeological study of their settlements. Their forces would raid Roman frontier towns along the Danube, and Rome wanted to put a stop to it.Led by King Decebalus, the Dacians attacked the Roman province of Moesia, located south of the Danube. During most of the next century, the frontier system fulfilled its function of guarding and regulating the borders, which in turn fostered deepening connections between Rome and the Germanic tribes who lived along the Danube.During the reign of Marcus Aurelius (starting in A.D. 161), state policy allowed increased numbers of barbarians (unarmed and in small groups) to cross the Danube and settle on vacant lands where they raised families, farmed, and paid taxes. Although Emperor Aurelian defeated the Visigoths, he surrendered the territory north of the Danube to them.Meanwhile, smaller tribes of barbarians beyond the Danube and the Rhine had been forming mighty confederations: the southern Germans into the Alemanni and middle Rhine groups into the Franks. In A.D. 260 the Alemanni broke through northern limes established by Hadrian, forcing the Roman frontier back to the Danube and Rhine.