Livonian Order is a very hard start because it's located right between Moscovy, Denmark/Sweden/Norway monster conglomerate, Poland, and Lithuania and all of them will want your land within the first 50 years after the start.
So, I tried several times and got brutally butchered by surrounding powers but finally managed to survive initial onslaught... Here are my thoughts:
1. The game suggests you to ally with Teutonic Order. While it's historically correct, in the game it's a death sentence. Most of the surrounding nations declare Teutonic Order as a rival meaning you won't have other allies and you're doomed. Better rival it too and delay the everybody ganging up on you event. TO won't attack you because their hands will be full.
2. Denmark with its unions with Sweden and Norway will eventually want Ösel via a mission and will come for your Livonian soul even if their relations to you are above +160 but the first action of the game should be improving relations with it to form a temporary alliance to make sure Lithuania won't attack you.
3. Improve relations with Poland and ally with it because even if Lithuania wants your blood it is destined to be PUd by Poland and by the time Poland will want your territory it's already your ally and you should keep it busy with wars to make sure they won't get some interesting ideas about your land.
4. Ally with Riga but fabricate a claim for an attack of opportunity if it's going to be forced out of all alliances you just annex it.
5. The initial expansion itself is not that problematic till Novgorod exists. Using missions you can get some freebies by fabricating a claim and taking Ingermanland and, may be, Neva. It needs to be done before Moscovy will grab them for themselves and they start to do it almost immediately. Getting a border with Moscovy early is a suicide, so you need to make sure you capture Novgorodian provinces as a buffer between LO and Moscovy. Also it's very important to keep Torzhok for Novgorod because it's blocking access from Moscovy to it's Pskov vassals. Then wait for Moscovy to make a piece deal first and take provinces strategically that there is a layer of Novgorod between LO and Moscovy. Normally it's Neva and Ingermanland that you take. This war must be fought with Denmark as an ally because you not only don't want to waste your troops but also it prevents Moscovy from grabbing too much of Novgorod lands.
6. Next war is against Moscovy. LO won't have allies in that but it must win... why? because LO is annexing Pskov and if you did everything right Moscovy itself cannot help Pskov because the access is blocked by their rivals: Lithuania and Novgorod. So you just daringly DOW Pskov/Moscovy with the CB of conquest of Pskov or Ostrov provinces. Take those provinces and wait a war score to tick to your victory. This war is very good not only because you took land but because you also get truce with Moscovy, which is extremely handy for your next campaign against Novgorod.
7. So, at this time you should have an alliance with both PL and DNS (Denmark+Norway+Sweden). At the first opportunity attack Novgorod and vassalize it. Moscovy tends to ally with Denmark at this point and right after Novgorod is gone Denmark will REALLY will want Ösel (-95 relation hit) and most likely break the alliance and select you as a rival... happy times... your force limit is only 9 + Novgorod vassal with strictly inferior troops gives about 8 and DNS combined is over 40, which includes OPd Swedish terminators.
8. Then the Judgement Day comes one way or another... I prefer to start it myself as an offensive war against Moscovy because when you succeed you have great options to feed your Novgorod vassal. PL should be on your side but even on my successful attempt it bailed out of the war after a costly manpower exchange with DNS and Moscovy. I was left alone against DNS and Moscovy but they had serious problems with war exhaustion. So, I outwaited DNS till it had enough and WPd out too. Continuing war with Moscovy despite heavy pillaging drove me bankrupt because I had to hire mercs above FL to make sure I won't be overwhelmed and I noticed Moscovy was also sporting an Army over the FL but due to higher tech I managed to finally beat Moscovy and restore Novgorodian lands almost completely. During the doomsday war with Moscovy I even managed to get 2 Prussian provinces from Teutonic Order when I saw it was attacked by Poland and left without any troops, so I just took freebies. Right after the big war ended I happily bankrupted but with way more manageable position than before and PL still allied to me.
So, what's your take on Livonian strategy? I succeeded survival on my 5th or 6th attempt... in comparison, starting as the Knights Hospitallers who has one province was way easier and I made a huge empire on my first attempt due to allied Venice. Here everybody is your enemy. Even Poland if I stopped keeping it busy with costly (for them) wars immediately tried to grab my lands.
So, I tried several times and got brutally butchered by surrounding powers but finally managed to survive initial onslaught... Here are my thoughts:
1. The game suggests you to ally with Teutonic Order. While it's historically correct, in the game it's a death sentence. Most of the surrounding nations declare Teutonic Order as a rival meaning you won't have other allies and you're doomed. Better rival it too and delay the everybody ganging up on you event. TO won't attack you because their hands will be full.
2. Denmark with its unions with Sweden and Norway will eventually want Ösel via a mission and will come for your Livonian soul even if their relations to you are above +160 but the first action of the game should be improving relations with it to form a temporary alliance to make sure Lithuania won't attack you.
3. Improve relations with Poland and ally with it because even if Lithuania wants your blood it is destined to be PUd by Poland and by the time Poland will want your territory it's already your ally and you should keep it busy with wars to make sure they won't get some interesting ideas about your land.
4. Ally with Riga but fabricate a claim for an attack of opportunity if it's going to be forced out of all alliances you just annex it.
5. The initial expansion itself is not that problematic till Novgorod exists. Using missions you can get some freebies by fabricating a claim and taking Ingermanland and, may be, Neva. It needs to be done before Moscovy will grab them for themselves and they start to do it almost immediately. Getting a border with Moscovy early is a suicide, so you need to make sure you capture Novgorodian provinces as a buffer between LO and Moscovy. Also it's very important to keep Torzhok for Novgorod because it's blocking access from Moscovy to it's Pskov vassals. Then wait for Moscovy to make a piece deal first and take provinces strategically that there is a layer of Novgorod between LO and Moscovy. Normally it's Neva and Ingermanland that you take. This war must be fought with Denmark as an ally because you not only don't want to waste your troops but also it prevents Moscovy from grabbing too much of Novgorod lands.
6. Next war is against Moscovy. LO won't have allies in that but it must win... why? because LO is annexing Pskov and if you did everything right Moscovy itself cannot help Pskov because the access is blocked by their rivals: Lithuania and Novgorod. So you just daringly DOW Pskov/Moscovy with the CB of conquest of Pskov or Ostrov provinces. Take those provinces and wait a war score to tick to your victory. This war is very good not only because you took land but because you also get truce with Moscovy, which is extremely handy for your next campaign against Novgorod.
7. So, at this time you should have an alliance with both PL and DNS (Denmark+Norway+Sweden). At the first opportunity attack Novgorod and vassalize it. Moscovy tends to ally with Denmark at this point and right after Novgorod is gone Denmark will REALLY will want Ösel (-95 relation hit) and most likely break the alliance and select you as a rival... happy times... your force limit is only 9 + Novgorod vassal with strictly inferior troops gives about 8 and DNS combined is over 40, which includes OPd Swedish terminators.
8. Then the Judgement Day comes one way or another... I prefer to start it myself as an offensive war against Moscovy because when you succeed you have great options to feed your Novgorod vassal. PL should be on your side but even on my successful attempt it bailed out of the war after a costly manpower exchange with DNS and Moscovy. I was left alone against DNS and Moscovy but they had serious problems with war exhaustion. So, I outwaited DNS till it had enough and WPd out too. Continuing war with Moscovy despite heavy pillaging drove me bankrupt because I had to hire mercs above FL to make sure I won't be overwhelmed and I noticed Moscovy was also sporting an Army over the FL but due to higher tech I managed to finally beat Moscovy and restore Novgorodian lands almost completely. During the doomsday war with Moscovy I even managed to get 2 Prussian provinces from Teutonic Order when I saw it was attacked by Poland and left without any troops, so I just took freebies. Right after the big war ended I happily bankrupted but with way more manageable position than before and PL still allied to me.
So, what's your take on Livonian strategy? I succeeded survival on my 5th or 6th attempt... in comparison, starting as the Knights Hospitallers who has one province was way easier and I made a huge empire on my first attempt due to allied Venice. Here everybody is your enemy. Even Poland if I stopped keeping it busy with costly (for them) wars immediately tried to grab my lands.