Editing Imperium (board game) (section)

== Description ==
''Imperium'' is a two-player game simulating a series of conflicts between the emerging Terran (human) Confederation and an immense and ancient alien empire, the Imperium. The Sun and nearby stars lie at the extreme edge of this alien space-faring civilization, and the Terrans struggle to survive and expand against this powerful state.<ref name="wd16" /> While the Terran player is in control of the entire Confederation military, the Imperial player represents a low-ranking provincial governor on the frontier, who is forced to petition the central government for reinforcements and is occasionally subject to its meddling.

When ''Imperium'' was published in 1977, its scenario was not connected to any other game. GDW published ''[[Traveller (role-playing game)|Traveller]]'' in the same year, but ''Traveller'' was at that point a system for running adventures in a generic science fiction setting, with no established background. However, as the company constructed the [[Imperium (Traveller)|Third Imperium]] as the default setting for ''Traveller'', the situation in ''Imperium'' was [[retroactive continuity|retconned]] into the ''Traveller'' Imperium's history; it became the First Interstellar War, the first of many wars leading to the overthrow of the Vilani Grand Empire of Stars (''Ziru Sirka'') by the Terran Confederation and the establishment of the Rule of Man.

The fold-out map depicts a nearby region of the Galaxy that includes important nearby stars as well as hyperspace jump routes between them. This sector forms a single province within the Imperium.<ref name="wd16" /> The map is printed on a dark background and is overlaid by a [[Hex map|hex]] grid. Each hex represents a half [[parsec]], which would require about 1.8 years to traverse traveling at 90% the speed of light. Along the edges of the map are tracks for marking turns and tallying resources. The map includes a number of commonly known stars, such as [[Alpha Centauri]], [[Procyon]], [[Sirius]], [[Epsilon Indi]], and [[Altair]], as well as a considerable number with more exotic names (mostly taken from the [[Sumerian language]]). Only a dozen stars have naturally habitable planets, although many more have planetary systems with outpost-capable worlds.

The game includes a variety of ship types, ranging in size from the small scouts and fighters to the mighty [[battleship]]s. The ship counters are blue for the Terrans and red for the Imperium. Each counter includes a set of ratings, the ship type, and a silhouette. The combat ratings give the Beam weapon combat factor, the Missile factor, and the Screen factor. Beam weapons are for close range combat, while missiles are best fired at long range or used for planetary bombardment. Beam weapons are slightly more effective, but missiles get to fire first. The screen factor represents the ship's capacity for defense. The following ship types are available for production: Scout ships, [[destroyer]]s; several different types of [[cruiser]]s, dreadnaughts, and battleships; stationary monitor defense platforms, missile boats, and "mother ships" (functioning as [[aircraft carrier]]s) with their [[Fighter aircraft|fighter]] squadrons; transport and [[Tanker (aircraft)|tanker]] ships. Ships with a black silhouette can perform a jump between stars, while ships with a white silhouette can only travel through regular space.

The two sides' ships are not mirror images.<ref name="SG"/> The Terrans generally have stronger ships overall and have the upper hand on beam weapons, while the Imperium favors missiles. Smaller Terran ships focus on beam weapons while smaller Imperial ships are more balanced. On the other hand, larger Terran ships are balanced while most large Imperial ships feature stronger missile ratings. But there are exceptions - both sides can build Strike Cruisers with high missile factors, and each side have at least one unique ship typ not available to the opposing side: the Terrans can build cheaper Missile Boats, while the Imperium can build heavy Attack Cruisers.

The available jump routes can significantly hinder the movement of a side's forces. Certain star systems act as bottle-necks, and can be used by each side as a defensive front. Two of the stars do not allow refueling, so tankers are required to leave these sites. Ships (excepting fighters and missile boats) are allowed to move at sub-light speeds across the hex map, and so can move directly from star to star without following the jump routes. However the movement rate of these ships is only one hex per turn.