In the 40th century the people of Terra can only go to the stars as mercenaries. On alien worlds Terrans fight brushfire wars and thereby help Central Control maintain peace within its vast interstellar empire.
Archs, who fight with relatively primitive weapons, are organized into Hordes, which fight on underdeveloped barbarian planets and
Mechs, who fight with more modern weapons, are organized into Legions, which fight on advanced, civilized worlds.
Although Norton doesn't give an explicit description of the size of Yorke’s Horde, information given in the story implies that it is roughly the size of a battalion (about 1000 men give or take several hundred).
It is a rapid response force meant to be incorporated into an alien army and it is able to carry out deep penetration missions, much like those carried out by Merrill’s Marauders in Burma in World War II.
The central plot device of Star Guard is that of a mercenary battalion betrayed and having to fight their way to safety. In that device Norton mimics Xenophon’s description of the March of the Ten Thousand in his work Anabasis, in which he described the struggle of Greek mercenaries fighting in the depths of the Persian Empire.
http://en.wikipedia.org/wiki/Star_Guard
