Hi,
1., I think, one of the key to earn major victories (or sometimes - simply survive...

) is the right composition of your core force.
I would suggest, that you have 3x arty (2x 105mm is possible - one from upgrade -, if you have spared enough points), hopefully you captured the tanks at Tolvajeri - if not, than go back, and play again - and you should have 3x Ski Troops and 2x Heavy Inf, 2x Light AA (without trucks), 2x fighters, 2x level bombers. At least, this was my composition. I had to sell/upgrade one of the truck of an arty to have enough command point, but it worth.
AT guns and Engineers do not worth the money/command points...
2., Always try to concentrate your forces and do not split up on to much targets. OK, here you will have to partly.

But still, focus always on that tactics. I put 2x 105mm in the middle north of the the woods and the 2x light AA to defend them. I fly the bombers and the fighters above them to lure the Soviet fighter here, and so I can shoot it down with the combined AA and fighter force. I put one of the heavy inf to the key points in the west and one in the east. The 3x ski troops will be put also in these 3 locations. The other arty goes to east. It will probably suffer from hostile arty, but still it is an essential asset there.
3., Having enough money. I you cannot efford these war materials, go back and replay the scns to make a better result by saving more money (or play it on easier difficulty).
- One tank of the enemy moves right after the beginning to north-northwest direction. With the ski troopers and the inf brought from Vipurii, it can be cut off and slowly destroyed from turn 2 on.
- Always use the ski troops, as firefighters and cut-off units, because they are so fast and can moving almost through everything!
- I also bring up the inf from the very southwest to assist in the battles at the western key point.
- I also move the inf, standing next to Kiviniemi to the east to help the others and concentrate the forces there.
- Try in the east to destroy, or at least strongly weaken the hostile gun as soon as possible (probably after annihillating the tank and the 2x heavy inf front of it).
- Use alwyas the help of the bunkers! They can shoot without retribution from the enemy. Try to lure the enemy next to them.
- Pay attention, that no hostile unit enters Vipurii, as the battle will be lost at that time. Also you have to hold 3x secondary VP's at once. If you loose 4, even if you would retake them, the battle will be lost.
- You can use the AA's later, when they have not so much work, to retake secondary VP's, if this are not endangered from near enemy units.
- I never try to destroy the fuel tank, as it takes horrible casualties. I deal with the bombers either.

Hint: there are 3x fighters on the map. After you defeated them (strongly weakening is enough), your bombers are free to herass the enemy.
I hope, this helps, I do not want to give the whole solution.

Anyway, because of the smart design, the battle is never the same.
I could beat this scn, even with the hardest difficulty (13 str enemy units) and instead a tank, an another arty - I modified the campaign to make it historical accurate - and even with that, I could make the victory. While capturing additional 5 settlements outside the Mannerheim line. I do not write this, to show how good am I ( I'm just patient - I replayed the battle so many times, until I found the right solution and succeded...), but to give faith, that you can do it too.
The pictures shows the original campaign setup:
ikbenrichard wrote:Hi,
It seems i cannot beat the mission Karelian Isthmus. Playing on normal difficulty.
I am kinda new to this game as in played a week or 3 now. So is there someone that can give me some decent tips?
Seems playing in defence or offense is both leading to defeat. Tried artillery, tried heavy inf and tried mass attack.
The 2 missions before this one i played rather well with a minimum casualties.