2020 · Games Workshop Ltd.
The 9th edition rulebook is full of changes and clarifications but essentially these new rules are, at their core, less ambiguous than the prior edition and do a good job at removing multiple interpretations. It also introduces a new Coherency rule and checks and Command Phase.
The New Coherency Rule - The 6” vertical limit has been reduced to 5” in the new edition (the height of a single floor of Sector Imperialis/Mechanicus buildings) and if a unit has 6 or more models then each model needs to be within 2” of 2 models now.
Engagement Range codifies the concept of “within 1″ of the enemy” into a single term for reuse across the rules, and also adds a new feature – in 9th edition it now has a vertical component (5″) allowing for fights across different elevations in ruins, over crates or around barrels.
Measuring distances now has a section of the rules all to itself. Unit strength and Destroyed units rules have been updated.
The Command Phase is brand new for 9th and consolidates a few different things into one phase of the game. Essentially everything that happened in the void between the start of a turn and the movement phase, the “before the movement phase” rules.
--from the publisher’s website
