Casus Belli is a 1-4 player game of space exploration, settlement, and conflict. Humanity’s vast empire, built over a millennium of interstellar expansion, fractured into four powerful factions, leading to a period of darkness. Now, with factions beginning to reclaim forgotten regions of space, new alliances, tensions, or wars may arise. Some planets are already inhabited by independent human colonies, reluctant to join but open to alliances. Each faction’s approach is guided by its unique ideology, influencing exploration, colonization, and encounters with alien technologies that can both advance and corrupt.
Starting in a fragile peace, tensions may escalate, triggering war only if a faction gains a casus belli. As hostilities break out, factions align and clash in major battles across ten rounds. At the game’s end, each faction scores based on their assets, with victory dependent on strategic positioning and alliances.