I’m probably too late, but I’m gonna share my experience, in case it will help you, or anyone in need.
Ok, so I’m a pretty mediocre player, with a heavy defensive approach in my style; and was able to win this scenario in 10:30 minutes (game time), in hard, with a FULL aggressive method.
Start choosing Vilnus, Kaunas and Seinai: the one with the Wonder, the city with University (Chemestry my man!), and the one in the far west with infantry. First thing is to make 4 trebs in Vilnus + Hoardings, and send them to the right of the city, together with the cavalry. Then create 2 trebs in Kaunas + Lechitic Legacy, and send them (together with the military of the city) close to Vytautas city in the middle of the map. Then make 1 treb in Seinai + Elite Obuch, and send both the treb and the infantry with the others from Kaunas.
Also, research crop rotation, send 3 lumberjacks to farm and 1 to get gold. Use the market to get all the resources needed.
Finally, send your initial/main army close to the castle of Grodno, but do not attack yet.
Ok, now groups and, maybe, hotkeys. Jadwiga herself in group 1, the rest of the initial military in 2, and the trebs in 3. Group 4 is the military combination of Kaunas + Seinai, 5 will be the 3 trebs of those cities. At last group 6 will be the cavalry from Vilnus (at this point start making more calvs with the 2 stables from the city) and group 7 will be the 4 trebs you are making.
First step is to conquer the city in the middle with groups 4 and 5. As soon as you gain control of that city send your troops inside, with the exception of a few archers. Since the Muscovy just joined the party, use those archers to agro them and run. With some luck, they will pursue them and leave Vilnus behind (not always work, tho).
At the same time a small infantry of Vytautas will attack groups 1 to 3. Finish them off, and star attacking the castle. After you gain control of the city research the upgrades in the blacksmith, and start making cavalry; also make infantry from Seinai and keep sending them to this main group. Immediately send them to Volkowysk (the one with archers, more at south).
And also, at the same time, send groups 6 and 7 by the northern passage close to the northeast city of Vytautas, but again, do not attack yet. Keep your troops before the river passage, because a large enemy group will soon pass there.
In the meantime send groups 4 and 5 to snipe the castle in the closest Vytautas’ city, in the east. Train more infantry from the city you just conquered to strength 4, and build more trebs, if needed. Use these troops to finish off any enemies nearby, but they will probably be killed by the large group that came from north + military already in the city + some Muscovy. Try your best to eliminate any siege you see.
At this point you may have already conquered Volkowysk, or not. In any case the Teutons will join when you get your 6th town. With some luck, they will be agro by some unit coming out of Seinai, and will pursue it for the entire south part of the map, in that classic teutonic speed. In some tries I didn’t almost fight with them, but in others they destroyed my economy and/or attacked Grodno.
Anyway, after taking Volkowysk, immediatelly send groups 1-3 to Ostrow (the one with the Pagan Shrine). At the same time, use groups 6-7 to attack the castle that they are close to. In my experience you can successfully take it, but usually you will lose some other city - Vylnus or that one you took first, in the middle. So groups 1-3 rushing to Ostrow will work as some sort of backup plan.
And there you have it.
Some things worth to point out:
- Get your military upgrades as soon as you will gather the resources. There is no precise order nor moment to that, in my experience.
- As you can notice above, not a single intention nor strategy was put on the defensive side. Full aggression. Maybe some onagers wil help?
- I didn’t use bombard cannon because I’m dumb and forgot they exist lol (¯_(ツ)_/¯). But they’ll probably be a good idea.
- KEPP MAKING UNITS!
- I didn’t mention it, but I also made a lot of Obuchs.
- Yes, this strategy will toll A LOT from your multitasking. For me, it was hell, but for some reason it worked.