The biggest changes to movement from ESR Second Edition to Series 3 are the introduction of the Regulating Unit and Cohesion.
The active Formation Directive dictates what the Regulating Unit must do, after a player moves the Regulating Unit, all other Units are moved to remain Cohesive.
Units are required to remain within a specified distance of each other or the Formation’s Reformation Area to be considered ‘Cohesive’, and may not voluntarily move outside of Cohesion.
Series 3 also expands Movement Priorities, setting a priority for each Formation Directive and Status. Opposing Formations with the same priority are still pro-rated just as in Second Edition.