Sorry if necoring but I just wanted to add some inisght for 1.29 Manchu update with ironman
vanilla game (yes, I actually played it without DLCs). In 1.29 there were some changes introduced (sigh) that makes Byzantium veeeery hard to play, but is definietly doable as per attached screenshot.
There are two strategies that seem to work:
- "Wait for it" strategy
- Aggresive stance strategy
The "wait for it" strategy is a strategy designed around exploiting geopolitical situation, but ultimately predicates on being lucky. In a perfect scenario Ottomas first mop Anatolia and then go for Albania, which triggers a large scale conflict as Venice is guaranteeing Albania's independence. In this scenario Ottos wil roll over Venice's dependencies in the Greece area and then go for Venetia itself. In my playtrough both Ottos' stacks went north to siege Venice and this was the opportunity I took: I immediately attacked them with my allies, Serbia and Bosnia, who contributed around 14k soldiers to the common cause. We took Balkans together with some Venetian's stacks who fled from the north just in time to welcome back the first of the two stacks Ottos sent north. After mauling the European side, together we embarked in Anatolia and finished the work. The only caution for this strategy is: don't tarry but also be patient. If you wait too long and if Venice starts loosing, they are likely to accept peace with Ottos. If attacked prematurely, one of the stacks sent north will turn around and go for Constantinopole.
The aggresive stance strategy shares commonalities with the YT guide, but since there are some changes like additional forts for Ottos, parts of the original strategy became obsolete. First of all, go and watch the YT guide as it will provide you some background necessary to understand this battleplan. But first things first, appease Burghers and Nobility in order to extract from them money, leaders and monarch points. Delete fort in Greece and schedule building more galleys in Morea and Constantinopole, while Achea should start training troops.
Simultaneously start improving relations with your future partners: Wallachia, Albania and optionally Theodoro + Imereti who will become your allies. Albania and Wallachia are key components of this scenario, while Theodoro and Imereti could contribute navy and some cannon fodder but most likely Ottos will start improving relations with them and they will be in the end unwilling to start a war with your enemy. Improving relations with Mamluks also should be beneficial, as they will give your subsidies during the war which will help you a little financially.
Move your navy and land units to Morea region. Navy actions will be the easiest: you should be able to use it for blocking straits. Deploy your navy to Aegean Sea with "attach friendlies" option selected. Upon entering the war, Athen's fleet will attach itself to you. If Theodoro and Imereti are with you, you can move your fleet to the Crimea region, attach them and start blocking straits leading from Anatolia to Europe.
Trickier part are land unit movements. You will be operating with 2 stacks. Send one, 11k strong, to Wallachia (you need access rights from Hungary), have them wait where Wallachian 8k stack is with "attach friendlies" option selected. The second stack, around 7k strong, should stay in Athens with the same option selected. When war is triggered, Wallachian stack should march to Edirne to lay siege and intercept any rogue Otto stacks that are on this side of strait- with navy blocking straits, they can only march to Constantinople where you can easily dispatch them (Otto stack around 12k) and go back to siege. The Athenian stack should besiege a fort in Macedonia region next to Edirne (Albanians and Athenians should be attached by now creating 14k strong stack).
While the siege plays out, you can play a bit with straits' blockage: you can move your ships to Aegean Sea, allow Otto stack to cross into Constantinopole, and cork up the bottle again- the AI should try driving that stack north to Wallachia and you can intercept it almost immediately. With sieges going on, recruit 1k units in Morea and Constantinople, and send them to conquer provinces without forts.
But as in each Byzantium playthrough, cards are stacked against you. Soon enough Ottos will gather force able to cross the straits and probably they will be able to do so soon before Edirne is taken. Now the Athenian stack is about to shine: if they by any wild chance secure Macedonian fort, you can move them to Edirne right away; if not, you have to dispatch them through a way around. Ottos will throw everything they got to prevent the fall of Edirne and thus, you will be able to see how OP they are. Your forces will be defeated, that's more than certain, but you should end up again with two stacks: Athenian 10k something strong and Wallachian around 12k. AI will now divide its forces sending them in small stacks (6k-8k) to different locations and as soon as your units are recovered, take this opportunity to maul them. If you are lucky and crafty, you should end up with warscore high enough to demand Edirne and thus securing your backyard (as long as your navy will do its job).
Most important thing: by securing monarch points in the earlier phase, you should be able to reach military tech level 4 before Ottos do and maintain this state for a few months securing your land supremacy, but as soon as Ottos got their tech up to 4th level, they will win any land battle where you don't have a 2:1 soldiers advantage (happens all the time; 20k my stack vs 15k Ottos crossing a strait and guess who's winning).