Quick Primer for Returning Players
This guide is for those who have played the previous CoH games but are new to CoH3. In this quick primer I explain the differences the latest title has, including information relevant to skirmish / multiplayer changes.
New features and major changes in CoH3 compared to previous titles
Tactical Pause
In single player, Tactical Pause is a new feature that is available in Coh3. By default, pressing Spacebar will pause the game entirely, but still allow the player to move the camera and issue commands normally to any of their units. All commands will be queued up appropriately, which can seen when selecting the units.
This makes the game far more accessible as an RTS, as it now means players can easily pause whenever necessary and take as long as they'd like to issue all their commands. As a bonus, it also works when viewing replays - while that may seem limited in usefulness, it can be helpful in understanding how an opponent plays. Pausing can even help determine if cheating is involved (Ex. showing mortars targeting exactly where units are despite no vision or clue being offered in-match).
Single Player Campaigns
The 'main' draw of the single player campaigns is the Italian Dynamic Campaign. This campaign takes place in the Italian theatre, allowing players to take control of US, UK, and Partisan forces. The campaign is called 'dynamic' as it is the first in the CoH series to take on an approach similar to what is seen in the Total War games. This involves an overhead map where 'miniatures' represent your armies and bases. Players will need to manage these, choosing what to build next and where to move on a turn-by-turn basis. When army representatives on the overview map collide with enemy forces, a skirmish battle may occur (in other words, the 'regular' RTS gameplay). The game map the player fights on is dependent on where the conflict occurred on the overhead map, and there are scripted missions for specific areas. Players can strategize in many ways, as they have the freedom to decide what kind of armies they want and where they want to push, but they will also need to manage their resources and battle lines carefully. Players also need to contend with keeping each commander happy, with each of the three representing USF, UKF, or Partisans. Objectives will often task them to help out one at the cost of another, and depending on what the player decides to do, they can gain or lose rewards from each 'faction'.
Another more traditional linear campaign is the DAK campaign. This follows the German campaign in the North Africa theater, and plays much more like how the previous game campaigns did where players need to play through successive missions that are broken up with cutscenes in between.
Skirmish / Multiplayer Changes
Battlegroups replace the old commander system in CoH2, and works more similar to CoH1's system. During matches you can pick your desired battlegroup, which then contains a 'tech tree' of sorts with diverging paths. Unlocking anything requires Command Points (CP) as usual, and just like before you earn these over time by dealing and taking damage. The diverging path of battlegroups means for example, picking A may exclude you from picking B on the same horizontal level. This means matches are more interesting as there's more decisions and exclusive choices players can make every match.
Breach is a new ability where certain units with grenades or flamethrowers can use this ability to target a garrisoned building and forcefully eject the enemy, while garrisoning the building themselves afterward.
Towing is a new feature where various heavy weapons, such as AT guns, can actually be towed by a truck/half-truck. This grants new levels of mobility not featured in previous titles, and makes the battlefield far more dynamic and interesting than before. Some heavy weapons cannot be move at all and are dependent on towing for mobility, and typically are bundled with a towing vehicle when produced.
Elevation is a new consideration where generally a unit from high elevation will have an accuracy bonus against units below them (this is represented with a yellow mountain icon for the high elevation unit). In other words, depending on the map certain areas like the top of a hill can be advantageous to fight from.
Quality of life changes such as auto reinforce toggles, auto-place base construction, being able to Retreat garrisoned units, and customizable controls.
Various tanks can transport troops via 'tank riding' (similar to transporting on trucks).
Some trucks/half-trucks have the Recrew Weapon ability, which spends a small amount of Manpower to crew an empty weapon on the field. They essentially spawn two soldiers from themselves, sparing you the trouble of sacrificing an existing squad's integrity to recrew a weapon.
Critical states against vehicles are less common, and overall have been reduced to simply 'Engine Damage' and 'Crew Shocked' states. No more abandoned tanks or disabled gun turrets.
The time-to-kill has been significantly increased (as in, things take longer to kill) in CoH3 compared to earlier titles, giving players more time to react to fights. This is mostly noticeable in how less lethal everything is in CoH3 compared to earlier titles - combat between units generally take longer as units don't die as quickly, and various area of effect damage have limitations such as model caps (the max number of individuals an explosion can damage at once).
The overall balancing of unit types has been improved, in the sense that lighter vehicles have a much larger role and do not become obsolete super quickly as they did in the past. Much more emphasis has been made to give each unit unique abilities or utility that make them worth keeping around even in the late game. 'Late game' tech and units are very expensive, meaning there is a real resource and time cost to building them. As such, the 'early' and 'mid' game stages last longer.
Veterancy has been greatly improved - it feels much more rewarding to keep units alive, and they feel far more impactful compared to newly built units. This is usually because nearly every unit gains a special ability at vet 1, and bonuses can be further improved for all factions.
Economy is fairly different in CoH3 - each territory point only creates one specific resource (ex. a fuel point only provides fuel), and the amount of resources you get is much lower (ex. +5 per minute). The resource points further away from both teams tends to grant significantly higher income, providing an incentive to fight over them.
Capture time of strategic/resource points are longer than previous titles.
Victory Point tickets go down significantly faster than they did in the past, especially if all points are owned by a player/team. This puts more importance and pressure on capturing VPs.
Overall match length have been reduced especially due to the VP changes - this is most noticeable in 1v1s where 30 minutes is considered quite 'late game', and 40+ minute matches are very unlikely.
Overall, for returning players to skirmish mode, the biggest thing to note is that the pacing has changed considerably compared to previous titles.