Arminius (a Latinized variant of a German name, which is unknown, but probably was not "Hermann") was the son of a Cherusci war chief named Segimer. As a young man, he was trained as a military leader and served as an auxiliary in the Roman army, probably fighting other barbarian tribes in the Balkan peninsula.
He eventually returned to Germany, where the Roman Empire had established control of the territories west of the Rhine and sought to extend its hegemony eastward towards the Elbe river, under the military governor Publius Quinctilius Varus. Arminius soon began plotting to unite various German tribes and to thwart Roman efforts to incorporate their territories into the empire.
In the fall of 9 AD, in the battle of Teutoburg Forest, Arminius and a his alliance of German tribes ambushed and annihilated three Roman legions totalling about 30,000 men commanded by Varus. The precise location of the battle remains to be established with certainty, but may have been near the hill called Kalkriese near Osnabruck. Varus committed suicide by plunging himself into his own sword, and the Romans never again attempted permanent conquest of any territory on the right bank of the Rhine.
After his great victory, Arminius tried for several years to bring about a more permanent union of the north German tribes so as to resist more effectively future Roman efforts at conquest, but did not succeed in the face of tribal jealousies. He also met the Romans in other battles, as they sought revenge for Teutoburg Forest. In 16, at Idistaviso, a Roman army commanded by Germanicus managed a victory over Arminius, raided the German settlements and even captured his wife Thusnelda. However, Germanicus gained no lasting benefit from his victory, as Arminius defeated another Roman force near the Weser River and compelled the Romans to withdraw.
A few years later, Arminius was murdered, allegedly by a member of his own family.
Largely forgotten for centuries except in the accounts of his Roman enemies, some of whom highly respected him for his military leadership skills and as a defender of the liberty of his people, the story of Arminius was revived in the late 19th century as part of the revival of German patriotism. In 1875, during the early years of the second German Empire and in the wake of the German victory over France in the war of 1870/71, a massive statue of Arminius was built on a hill near Detmold, about 75 miles from the presumable battle site, where it is a major tourist attraction.
Arminius is also the Latinized form of the name of Jacob Hermann (1560 - 1609), a Protestant theologian who formulated a doctrine of grace that stressed free will rather than predestination. See Arminianism.