Shalmu is an inhabited planet in Sector Alpha Crucis.
"Shalmu" is its name in one of the languages of its most technologically advanced civilization.
That civilization was in a bronze age when discovered.
Sporadic trade progressed it to iron.
In Flandry's time, a combustion-powered technology spreads the advanced civilization across Shalmu.
This process is slower than on Terra because Shalmuans are less inclined to exterminate or exploit each other.
The Terran Empire protects Shalmu from barbarians.
The Terran Naval base is on a barren planet elsewhere in the system.
However, the small marine garrison on Shalmu and spacemen visiting the planet on leave bring traders who do business with both service personnel and natives.
Some Shalmuans work for extraplanetarians or gain scholarships for outsystem education.
Shalmuan taxes are metals, fuels, food or art.
The Imperial resident does not interfere with native cultures and suppresses wars and bandits with his marines.
Terran law curbs the arrogance of young Imperials.
Sector Governor Snelund increases taxes and militarily enforces payment. Then he instructs armed Shalmuans to catch others for the barbarian slave trade. This decree is enforced by mass crucifixions.