Units may move from their Base to a Battlefield. 1. Units cannot Move to a Battlefield that already has units from 2 other players present, or where a Combat is ongoing that has 2 other players as participants. See rule 447.2. For more information on valid destinations for movement.
§ 144.4.a Core Rules PDF (officieel)
§ 144 Units have the Inherent Ability to perform a Standard Move.
§ 144.4 The Destinations where Units can Move to with their Standard Move are restricted:
