1. No coal, so no ironclads to protect your coast... ...seems the designers of this challenge have thought of everything (no coal even in Shakas and Ragnars land, only far, far away in Khans backland)
2. Ship of the lines (SoLs)... ...are the answer... ...build them in great quantitiy and you can keep your shores clean. After Stalins innitial invasion, I had some frigates promoted on scouting checking high seas and a stack of 6-7 SoLs with 4-5 frigattes on each side of the continent
3. Get the circumnativation bounus, thats important. If Stalin gets it, then it might be impossible to defend due to slow SoLs.
4. Promote your about half of your SoLs on navigation, that gives you 5 move togheter with the circumnavigation bonus, rest along the strength line, to pick of Stalins SoLs later. Strength 4 is goal here to have odds of 80%+ in open water
With that como, I managed to keep my shores rel save. Stalin usually brought stacks of 6-8 gallons and 3-5 frigates, later additional 1-2 SoLs. If there are stacks of 15+ gallons, simply kill the SoLs and frigates and block their way, then pick them off during several turns. Just ALWAYS replace naval losses, you NEED 10+ ships to do so successfully.
Sometimes some gallons managed to break through, because they were so numerous and decided to attack single frigates on sucide runs to break my lines, but never more then 3-4 of them managed to disembark units after the innitial landing and these were easy pickings with rifles. After thinking about it, I guess I sunk 100-150 ships, loosing only 10-15. After a while, they are so highly promoted, that you even can kill enemy SoLs with odds of 80%
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I´m about to take Ragnars capital within the next turns btw., but from now on it´s going to be painful, because he has infantry since some turns and I only cannons, grens and rifles... ...but at least I have lots of them
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I will post a save and some picks after I played the next session and took Rangars capital (only doing 3-4 turns now per session, because each turn takes ages)