After my first test of V4 rules I have tried to put together some changes in a summary. I might have misinterpreted some of the rules, but to write it down here as I remember it will help me and maybe others to transition into the new system.
Read the battle report here
Overall I like the changes to the core rules and the old rich detailed army lists are still there in EW and LW. Regarding MW I'm not at all convinced, as the army lists seems very thin of units and the new point system has less detail for small upgrades and adjustments.
Who takes first turn
There are now 3 ways to choose attacker, but in many cases I think it will come down to a dice roll. I think this an open field for some "house rules".
there are six standard scenarios and they have less special rules than previous. But most things are similar to v3.
All units must deploy in command of their leader (15cm or 20cm). This results in more compact deployment overall. Also gun team command sections and staff teams are not deployed (only guns deploy).
The benefit of having an even number of platoons is now gone! You must no longer test for company morale, but if the company has less than 2 combat platoons or HQ units on the table it automatically retreats the battle. Platoon tests are made if the platoon have taken any causalities and have 3 or less infantry teams left, while guns and tanks test if they have two or less teams left (guns only counting gun models). Tank terror seems gone!
Infantry is now faster with a standard 20cm tactical move, while tanks now always move 25cm regardless of terrain if they want to shoot in the shooting phase. Both tank and infantry can Dash at faster speeds (tanks taking cross checks for terrain), but then loose the ability to shoot and assault. There is a few ways to alter this by tactics (see below).
This is a big difference to v3. Now skill and morale rating influence the units ability to take additional moves. With a skill or morale check one of the following extra maneuvers can be made by any team in command of the unit leader (in his own unit):
Dig in (skill, instead of movement): The unit digs in if the roll is successful. Regardless if it is successful or not the unit shoots as if it has moved, is concealed and may GtG. It may not assault.
Blitz (skill, roll before movement): Move 10cm without loosing RoF. But if check is failed, the unit does not move and suffers an +1 to hit in shooting. Assault is not allowed in the assault phase.
Shoot and scoot (skill, roll instead of assault): May move 10 cm, exactly as the old storm trooper rule.
Follow me (morale, roll after movement): Allows an additional 10cm move after ordinary movement. Regardless if it is successful or not the unit cannot shoot, but can assault in the assault phase!
Cross here (auto-success, movement): All units in command of the unit leader adds 1 to their skill check for crossing terrain/obstacles. But the unit cannot shoot or assault.
The German storm trooper rule allow the Germans to take a shoot and scoot maneuver in the assault phase in addition to having taken another tactic move in the movement phase!
Also, trained armies (like hero soviet) benefit more from their higher skill rating despite only being trained! Fearless armies will also be more likely to reach assault range with "follow me"!
Higher command is now considered a separate unit and will confer morale re-roll to any unit within command distance. The CiC will not flee the battle if the unit using his re-roll fail its test.
To-hit ratings are same as v3 but the shooting player choose which teams are hit, starting with "unconcealed/close range" teams. The target player may then try to swap all hits taken on a team on 3+ for another valid target within 15cm. Aircraft are now always hit on 5+ rather than the skill of the AA unit.
All infantry teams and guns always starts the game dug in and GtG. All guns (incl. immobile) benefit from concealment in foxholes. All infantry teams, light and medium guns always have 3+ save. Heavy and immobile guns always have a 4+ save. Aircraft have a 3+ save (making it much harder to destroy), but are permanently destroyed if it fails. Tanks work as per v3.
Yo can aim wherever you want as long as spotter or artillery team can see the aiming point. "Range in" and "to hit" are "inverted", meaning that it is the spotters skill that counts for ranging in and the targets training that decides if the team is hit or not. Repeat bombardments range in automatically and the opponent must re-roll inf and gun saves! This makes artillery overall much deadlier against soft targets. Also add that firepower is now better for all FP 4+, 5+ and 6+ guns! However, all artillery now have lower AT ratings so don't expect artillery to shoot out tanks anymore.
You can now only assault with teams that are 10cm of an enemy team, or if you can get into base contact with a friendly team that just assaulted with a 10cm move. You must be in base-to-base contact with the enemy or a friendly team in base contact to hit the opponent team! All teams may now shoot at tanks in assaults (using side armour) or use tank assault rating 2 at top armour (or higher if they have a special rule that says so). Remember that only teams in base-to-base contact can act in assault. Otherwise assault and defensive fire is mostly as per v3.