Afrikaner-ethnic world with very high gravity and intense heat. CoDo convict-transportees later become a slave caste. Extreme conditions and aggressive native life result in a very low survival rate, producing extreme selective pressure that eventually result in an immensely strong, physically tough population.
After the breakup of the CoDominium and the virtual depopulation of Earth, Jarnsveld's Jaegers (JJ) found its original functions more and more redundant as the local militias and national conscript army grew in size and effectiveness.
Gradually it assumed a new role as an elite, all-volunteer cadre and rapid-deployment “fire-brigade” unit. During the era of interstellar anarchy immediately after the Great Patriotic War, it was used with decisive effect in several stellar systems in Frystaat's immediate neighbourhood.
The Republic of Frystaat initially followed a policy of limited trade and alliance against any power strong enough to rebuild interstellar unity. With the rise of the Spartan hegemony, the Landholders decided that a change of tactics was in order. No possible combination of independent systems could face the former CoDominium fleet, which had transferred its base and allegiance to Sparta. Instead, the Republic voluntarily offered allegiance and actively assisted Sparta in extending the dominion that eventually became the Empire of Man, in return for a high degree of internal autonomy.
The most potent instrument of that assistance was JJ. Small, but highly trained and well-equipped, JJ was used not in conventional main force operations but as an instrument of irregular warfare. Missions ranged from subversion and assassination through counterinsurgency and anti-terrorist work. The unique characteristics of the settlers of Frystaat made them even more formidable than their high degree of training and esprit de corps warranted, particularly in the small-unit infantry operations in which they specialized.
In the present era, JJ has been actively engaged in attempts to suppress secessionist movements. They have also acquired the distinction of being the only unit ever to fight a successful ground action against genetically engineered Sauron troops without superiority of numbers or firepower....
Sources: War World, Vol. I: The Burning Eye,