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Oni Lord,
Other than the tactics that I suggested, I also put the game speed to "1" during combat situations, and saved the game every time I got kills. In general I used flanking and crawling, trying to stay out of enemy lines of sight.

"Oni Lord",
It was a lot of fun because the mission seems designed for your starting squad to get creamed, especially if you played on Hard, for five reasons:
First, the general context is the start of the 1939 Soviet-Finnish Winter War, when there were alot of Soviet casualties. I recall that the final tally of that war was a abot under 25,000 Finnish casualties and a bit over 140,000 Soviet casualties. (not counting wounded or prisoners on either side). The mission designer intends to show this difficult challenge, naming the mission "Cannon meat."
Second, there is a line of AP mines stretching across the whole map. I'm not sure if the designer intended for you to be able to crawl through the tiny gap in mines on the far edge of the right side of the map, but maybe you could still use AT grenades to bust through the mine field.

Third, the enemies are in trenches and on Hard at least they can see you before you can see them, and it doesn't take long for them to wipe out your squad if you try to run or crawl through their fire.
Fourth, when your squad is wiped out, you get a new squad, which almost never happens in MOWAS2 missions. The new squad has a flamethrower tank, sappers, and two MG armored personnel carriers who are able to easily clear through the enemy's second line of defense.
Fifth, when you beat the mission even with no casualties, the ending sequence says that Andrey buried his friend Lyosha from your starting squad with other soldiers from that starting squad.

You are genius, my friend

To get 0 losses in the first part of the mission on Hard, I carefully maneuvered through minefields, staying closely to the right edge of the map. It seems that if I use soldiers one at a time, make them crawl straight by the map's edge, and don't have them carrying grenades, they are less likely to hit a mine. This way I put my SVT rifleman next to a pine tree's trunk well protected by branches, and had him snipe the trench on the right where the enemies stand. The SVT is a semiiautomatic rifle, so he can shoot 10 bullets in a round quickly, and his hits are stronger then an LMG. If enemies start shooting back, I have him duck after each good shot he makes. This way I cleared the trench on the right side, and winning became somewhat easy using flanking.

The "No Molotov" mission is here:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1838403078

I beat the RKKA campaign's mission, called Cannon Meat, on Hard with 0 losses. It seems that the mission designer actually intends for you to lose your first group of troops with the hero, Lyosha, and then get reinforcements, because the victory sequence says that Andrey buried Lyosha and other soldiers from the first wave. Plus, when your first group of soldiers dies, instead of losing the mission like normal, get a second group.