The stacking limit for a grid space is 5 Military Units on the map, 2 Units on Location Cards, and unlimited in orbit.
Worker Units do not count towards the stacking limit, and stacking limits can be ignored while Workers are leaving a Utility to become Civilian Units (see Section 13.2).
Marches (a battle-ready advance of Units on the map) may ignore stacking limits, and there is no penalty for overstacking a space during a March.
Movement on the Planet Surface
Units on the map can only change grid spaces via Military Orders or during Bonus Military Actions. (Occupying or vacating a Utility during an Industry Action or appearing on the map for the first time does not constitute a change in grid space.)
Note the following terrain restrictions:
• Human Units cannot cross or enter the North Pole (because of its extreme heat).
• There are no restrictions on humans entering the South Pole.
• Ground Units responding to a written Order cannot cross cliffs (black lines or shadows), and can only cross white lines. Three Military Bonus Actions (Disperse, Hide and Pre-emptive Strike) allow Units to ignore cliffs, but not to ignore the restriction on entering the North Pole. Air Units are unaffected by cliffs.
• Moves and Marches have different distance limits (described in Section 17)
• Units may travel to or from the Cryos Moon, via the Cryos Shuttle, a notional space between G6 and the Moon. Moves and Marches involving the Shuttle must start or end on the Shuttle.
• Units, Shields and Utilities cannot be built and Civilians cannot be mustered in the Shuttle.
• Some Skill Cards modify these terrain restrictions.