To beat the first level's Beach landing mission (im still devising a complete way to win the full game; Im stuck at the second mission)
Send one squad of your squads to the Leftest part of the map, right next to a trench. At the same time, move your other two squads to be inbetween the two weakest trenches (the ones that dont have arty/ a second line of machineguns and death)
As the squads you sent inbetween the trenches take and give back fire (we'll call these squads b n c.) your A squad should have little problem taking the first trench, as Your pre-determined battleship arty will kill most of them. Now this also means you shouldn't run A squad into the trenches as thy'll be blown to pieces.
Now, hopefully your flamthrower unit is ok! because they will be of great use to destroy theenemy mortars behind the first trench. In case they dont survive, Get a squad to attack the mortars. Then, Take control of the mortars and attack the second trench! godspeed!
Now make sure you have
B squad to finish off The first trench
B+C moved into the second trench and take it
A squad is entrenched
If one of these steps aren't completed, you will fail (at the very least slowly)
After the enemy charges into the first trench in an attempt to retake it, and you have defeated them (the infantry easily, The tanks impossibly) Move all squads into the second trench. YOU MUST TAKE IT!
Then, in an act of sacrafice, scourge the dead enemies for anti-tank grenades. When one of the tanks aren't looking, tell your designated grenader to (sneakily) throw a grenade. (WARNING; @/3 grenaders will not survive)
Now after you have defeated the Tanks, YOu should have realized you have 2 extra squads. We'll call them X and Y.
As the A.I infantry and your own attack the main battle lines, move X and Y into the enemies trench and have them thrwo all the grenades!
After a heroing bloodbath where you have between one and two squads total of men alive, the enemy will retreat because they got blood on their suits and need to look good for the victory party
you have decimated their defenses and they have limited supplies.
Good luck on mission 2!