history

The Imperial German Bodyguard, the Batavi, were one of the most elite military groups of that time. They also seemed to have had a strong moral code as they appear to have taken very firmly principled moral stands that sometimes put them in harsh opposition to the political dynamics that eventually fractured Rome and its empire. Loyalty, bravery, and strength. Those were some of the core features of the Batavi.

https://en.wikipedia.org/wiki/Numerus_Batavorum

The guard was disbanded briefly after the Battle of the Teutoburg Forest,[citation needed][18] and was finally dissolved by Galba in 68[3] because of its loyalty to Nero (ruled 54-68), whom he had overthrown. The decision caused deep offense to the Batavi, and contributed to the outbreak of the Revolt of the Batavi in the following year.[19] Their indirect successors were the Equites singulares Augusti which were, likewise, mainly recruited from the Germani. They were apparently so similar to the Julio-Claudians' earlier German Bodyguard that they were given the same nickname, the "Batavi".[20]

Tacitus (De origine et situ Germanorum XXIX) described the Batavi as the bravest of the tribes of the area, hardened in the Germanic wars, with cohorts under their own commanders transferred to Britannia. They retained the honour of the ancient association with the Romans, not required to pay tribute or taxes and used by the Romans only for war [...]

Tragically, many of them fell victim to political intrigue and other abuses, as is often the case in a world ruled by powerful political entities. The Batavi were also some of the few forces that have ever been able to achieve significant victories at that time against the Roman Empire, although not without employing some of the Romans' own military tactics against them. Whether that should diminish their victories or be a testament to their military strategy acumen, on top of mere strength and bravery, I am not sure.

Either way, despite only comprising a tiny portion of Rome's military forces, they seem to have been able to hit far above their weight, so to speak:

The Batavi auxilia amounted to about 5,000 men, implying that for the entire Julio-Claudian period, over 50% of all Batavi males reaching military age (16 years) may have enlisted in the auxilia. Thus the Batavi, although just about 0.05% of the total population of the empire in AD 23, supplied about 4% of the total auxilia i.e. 80 times their proportionate share.[citation needed] They were regarded by the Romans as the best and bravest (fortissimi, validissimi) of their auxiliary, and indeed of all their forces.[3] In Roman service, they had perfected a unique technique for swimming across rivers wearing full armour and weapons.[4]

https://en.wikipedia.org/wiki/Revolt_of_the_Batavi