I also have a "Colonial Constabulary" attached to the Colonial Office. This is optimised for peacekeeping-counterinsurgency. While th
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The Colonial Constabulary-whose name was recently changed to Planetary Constabulary for PR reasons but is still often referred to by it's older name-is a orginization somewhere between police and military. It is organized into Constabulary brigades of about 3000 each which include one thousand "light infantry"(garrison, patrol, escort), two hundred men in "advanced probe teams"(recon)100 men in "heavy weapons teams"-never very heavy, after all thats the armies job. Their are also 700 enginners, two-hundred medical, 400 enginners(for building things),300 gendarmes(police)and 300 diaster-relief. Besides the brigades their are a pool of "specialists"-with whatever odd skills are available and their is the Inspector's branch-which provides intell. However most Constables have served in several capacities during their career and are comfortable being suddenly used in another role-they are trained to be versitile.
This is a "typicle" Constabulary brigade-composition varies widely.
The Constabulary often work with the IISS-but have something of a rivalry with them. However the Constables maintain their own mystique. Indeed some of the most famous publications on such subjects as terraforming, colonial devlopment, survival, or whatever might be thought of are from the Constabulary.
The Constabulary is also famous for keeping the law in places where the Imperium's only representatives for hundred's of miles are a few constables. This does actually happen-usually on a world with a government that is incompletely developed-classically, a new colony: after all the Imperium prefers that local functions be done locally if possible.
Though enemies of the Imperium often refer to them as "lackeys of Imperialism"-not totally without cause, they are generally polite and diplomatic and work well with local people, except for those that happen to be enemies of the Emperor. Quite commonly a world will request their presence to keep the peace, help in a disaster, suppress a local rebellion(not necessarily a good idea-one of the first rules of civil war is that the first party to call in outsiders is not likly to be loved-and in any case the Imperium might decide that the present ruler is a useless incompetant), or simply to train local troops and emergency services.
The Constabulary is highly regarded even among the Imperium's enemies.