The Great War: Western Front

Campaign

Don't be afraid to do nothing on a turn to build up funds, the game is very long term and the enemy is not super aggressive. You need to spend money to replenish your troops after fights, so if you go into them broke then you're going to run into the red.

Don't mix multiple nationalities of troops together, it gives a "disunity of command" debuff for morale.

Generally speaking what troops you have are what you get. You can build new planes or (later on) tanks, but infantry only comes from certain technologies or random events.

Supply Depots are the most important tile improvement you can make. Individual troops will carry a small amount of supply into battle but a depot will make that number exponentially higher. If you want to fight properly you need a depot on a tile, so put them down all along the front or you'll quickly find yourself running out of supply during the fight.

The game has a detailed trench system and you'll see the enemy using it to create webs of networked trenches all over capture points. Don't do this. Enemies in the open will get mulched extremely quickly by fire from trenches, so you want to force an attacking force to go over the top in order to advance. Make small lines of trenches separated by a good distance to make them go over. Ensure that you have units spread out enough that a light arty barrage or two won't completely lock down your entire defensive force.

When on attack you want to take advantage of their stupidity and focus almost entirely on stuffing troops into the ant farm of their trenches to melee attack each trench one by one. Make sure you give commands to have your troops go directly from trench to trench or they might try and get out to run over to your move command and get slaughtered immediately.

Heavy artillery is for breaking up massed infantry pushes while light artillery is for covering your own pushes. Heavy arty gives sporadic suppression over a small area but does direct damage while light does minimal damage but suppresses wide swaths of land. You want start every advance by dropping light arty all over the enemy trench system to get their heads down and then pressing into it, including hitting then trenches while the arty is still going. That being said, light arty can also make for really good defensive play; get a few squads together to counterattack in the open and suppress the advancing squads to allow your guys to freely destroy them. Similarly the heavy arty can be used to burn down troops that are in normal trenches where the trenches around them are saturated, leaving them nowhere to safely run.

You only lose "morale" (score) if a squad is destroyed, so don't be afraid to retreat even moderately damaged squads. You have a huge number of them to use and they are cheap, use them all. This is especially important in melee trench combat; you can't retreat an engaged squad, so if your squad is at 2/3rds health then you should be putting them into a firing trench rather than using them on offense because if they come in contact with a full health squad that is a guaranteed morale loss for you. If they are below half health just fully retreat and replace them.

Planes are often not worth it. They are good to have as a backup on high-risk tiles but they are expensive to use compared to heavy artillery. On the other hand, observation balloons are pricy but will often save your ass by mapping out enemy locations or warning of an impending attack.

Emplacements like HMGs or arty can be destroyed with heavy arty or planes, but it's more efficient to use light arty to suppress them to get men in the trenches then get them close enough to throw grenades at it, which they automatically do if its in range. The last time I played it had this thing where troops would only reliably throw grenades if they are running past an emplacement in the trench, so if they aren't throwing them you can tell them to move back and forth between trenches to make them throw.