The next civ I plan to play is the Ottoman empire. Here are my thoughts on how to approach them (having not actually played them yet, at least not since they were designed as a naval civ I think) and if anyone has their own thoughts please share for everyone's benefit.
Tanzimat
Completing a Trade Route grants +150 Science and Food to the origin City if international, or Culture and Gold if internal. Bonuses scale with Era.
Janissary, replaces Musketman.
+3 Combat Strength and +1 Ranged Combat Strength. +25% Combat Strength when attacking and starts with the March (unit will heal every turn, even if it performs an action, but receives a -15% Combat Strength penalty when defending) Promotion.
Siege Foundry, replaces Forge.
3 Production and 1 Science. +50% Production towards Siege units. All Siege units trained in the City receive the Volley Promotion for free. Nearby Iron and Copper provide +1 Production and +1 Gold. +2 Production from mines worked by this city. When you construct a Unit in this City, gain Science equal to 20% of the Unit's Production cost. 1 Maintenance.
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UA/UU/UB discussion:
First, the UA. The completion bonuses for the trade routes seem like they are in the ballpark of being about as valuable as the normal per turn trade route yields. In other words, you might see something like 5 gold, 2 science, 3 culture over 30 turns for a trade route in the ancient era and that is pretty equivalent to the completion bonus of 150 science/food or 150 culture/gold that the UA gives.
This makes it very important that the trade routes you send actually complete (not pillaged or interrupted by war) and you might also favor trade routes that are particularly low on the number of turns required to complete as long as those trade routes aren't significantly worse than the longer options. This might push me toward using internal trade routes rather than international ones as they should be much easier to protect, or maybe using international routes to nearby allied CSs or to nearby civs who I do not think are likely to DoW.
Also, since my trade routes are essentially twice as strong as a normal civs when taking into account the completion bonus, Petra and Colossus might be particularly good wonders to aim for.
The UU doesn't seem particularly tricky to use- a musketman with increased CS and RCS, march, and +25% to attacking is quite strong. Probably a good idea to pair at least some of them with medic I/II to increase the strength of march- maybe half go for the medic line and the other half work toward other strong promotions.
The UB, on the other hand, has some interesting incentives aside from the extra base production/science. +50% production toward siege units and siege units start with volley almost makes siege units an honorary UU of the Ottomans. In fact, it might make sense to spam siege units and not bother with the archer line at the beginning of the game and instead use siege units as an all-purpose unit/city attacker. If you look at the ranged unit and siege unit available throughout the game the siege unit either has greater or equal RCS while costing equal or less than the ranged unit when you apply the 50% production reduction. Aside from having worse mobility when in enemy lands (but only outside of rough terrain) compared to ranged units and admittedly worse promotions for straight unit attacking, the siege unit is probably a better value production-wise than the ranged unit. This might be especially true before the Janissary is available because once the Janissary is available any ranged unit you have that does not have a 4th tier promotion like march is sort of outdated and might not be worth upgrading. So I might plan on having an early army comprised solely of siege, melee, and some mounted units.
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General plan (victory condition, policies, etc):
I think Progress is probably the least incentivized opening policy. The more cities you settle the more you are diluting your on-completion trade route bonuses and the Ottoman kit doesn't have anything in particular that makes it easier or stronger to go wide than the average civ (maybe you could argue that the extra production/science on the foundry can help with wide some). If circumstances dictate that wide is better for some reason then I'm sure it's viable but all things being equal, it wouldn't be my plan.
I could see Tradition being used and leveraging the extra science/food or culture/gold from the trade routes to boost your capital quite a bit.
However, my view is that Authority is probably the way to go. Having a largely puppet empire means your completion bonus on trade routes is still a major contributor to yields. Also, if I am planning on having a LOT of siege units around I may as well use them for their primary purpose- taking cities! If I'm going to take a bunch of cities I may as well use the opening policy tree that will benefit that path the most.
With that in mind, my intended victory condition will likely be domination (or a win via culture/science/diplomacy by "default" after wrecking most of the competition).
I see less clear reasons for opting for a particular renaissance tree. Depending on how close I am to capturing a religion (I typically don't try to found one of my own if I plan on conquering my neighbors anyway) fealty may make sense, or if it looks like a domination aided culture or diplomacy victory is the best route then Artistry/Statecraft might be the obvious choice at that point.
Similar situation for the Industrial trees. Depending on how good or bad my conquering has been going, Imperialism might make sense or perhaps it will be time to pivot to Rationalism to get going on a science victory or Industry as a more all-purpose tree.
There are some interesting ideological policies for the Ottomans. In Freedom, the +2 trade route policy would be quite strong as well as Transnationalism ( Each turn, there is a chance that a Corporate Franchise will appear in a foreign city. Global franchise maximum increased by 20%.)- if I am unable to spread my corporation via trade routes for fear of them being pillaged and losing my completion bonus then having an alternative way for the franchises to be created could be nice.
In Order, Nationalization (Corporate Offices (up to your Global Franchise limit) function as Franchises. Foreign Franchises no longer benefit your Corporation.) could also solve the problem of having a tough time spreading franchises while Iron Curtain ( Free Courthouse upon city capture. +250% food or production from internal trade routes. City connections generate +5 Gold and Production.) could be nice if I am using a lot of internal trade routes.
Autocracy is overall just strong when domination is the goal but I don't see anything that synergizes with the Ottomans in particular.
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I'd be interested in hearing how others would play the Ottomans, or how they have played them in the past!
Tanzimat
Completing a Trade Route grants +150 Science and Food to the origin City if international, or Culture and Gold if internal. Bonuses scale with Era.
Janissary, replaces Musketman.
+3 Combat Strength and +1 Ranged Combat Strength. +25% Combat Strength when attacking and starts with the March (unit will heal every turn, even if it performs an action, but receives a -15% Combat Strength penalty when defending) Promotion.
Siege Foundry, replaces Forge.
3 Production and 1 Science. +50% Production towards Siege units. All Siege units trained in the City receive the Volley Promotion for free. Nearby Iron and Copper provide +1 Production and +1 Gold. +2 Production from mines worked by this city. When you construct a Unit in this City, gain Science equal to 20% of the Unit's Production cost. 1 Maintenance.
--------------------------------------------
UA/UU/UB discussion:
First, the UA. The completion bonuses for the trade routes seem like they are in the ballpark of being about as valuable as the normal per turn trade route yields. In other words, you might see something like 5 gold, 2 science, 3 culture over 30 turns for a trade route in the ancient era and that is pretty equivalent to the completion bonus of 150 science/food or 150 culture/gold that the UA gives.
This makes it very important that the trade routes you send actually complete (not pillaged or interrupted by war) and you might also favor trade routes that are particularly low on the number of turns required to complete as long as those trade routes aren't significantly worse than the longer options. This might push me toward using internal trade routes rather than international ones as they should be much easier to protect, or maybe using international routes to nearby allied CSs or to nearby civs who I do not think are likely to DoW.
Also, since my trade routes are essentially twice as strong as a normal civs when taking into account the completion bonus, Petra and Colossus might be particularly good wonders to aim for.
The UU doesn't seem particularly tricky to use- a musketman with increased CS and RCS, march, and +25% to attacking is quite strong. Probably a good idea to pair at least some of them with medic I/II to increase the strength of march- maybe half go for the medic line and the other half work toward other strong promotions.
The UB, on the other hand, has some interesting incentives aside from the extra base production/science. +50% production toward siege units and siege units start with volley almost makes siege units an honorary UU of the Ottomans. In fact, it might make sense to spam siege units and not bother with the archer line at the beginning of the game and instead use siege units as an all-purpose unit/city attacker. If you look at the ranged unit and siege unit available throughout the game the siege unit either has greater or equal RCS while costing equal or less than the ranged unit when you apply the 50% production reduction. Aside from having worse mobility when in enemy lands (but only outside of rough terrain) compared to ranged units and admittedly worse promotions for straight unit attacking, the siege unit is probably a better value production-wise than the ranged unit. This might be especially true before the Janissary is available because once the Janissary is available any ranged unit you have that does not have a 4th tier promotion like march is sort of outdated and might not be worth upgrading. So I might plan on having an early army comprised solely of siege, melee, and some mounted units.
--------------------------------------------
General plan (victory condition, policies, etc):
I think Progress is probably the least incentivized opening policy. The more cities you settle the more you are diluting your on-completion trade route bonuses and the Ottoman kit doesn't have anything in particular that makes it easier or stronger to go wide than the average civ (maybe you could argue that the extra production/science on the foundry can help with wide some). If circumstances dictate that wide is better for some reason then I'm sure it's viable but all things being equal, it wouldn't be my plan.
I could see Tradition being used and leveraging the extra science/food or culture/gold from the trade routes to boost your capital quite a bit.
However, my view is that Authority is probably the way to go. Having a largely puppet empire means your completion bonus on trade routes is still a major contributor to yields. Also, if I am planning on having a LOT of siege units around I may as well use them for their primary purpose- taking cities! If I'm going to take a bunch of cities I may as well use the opening policy tree that will benefit that path the most.
With that in mind, my intended victory condition will likely be domination (or a win via culture/science/diplomacy by "default" after wrecking most of the competition).
I see less clear reasons for opting for a particular renaissance tree. Depending on how close I am to capturing a religion (I typically don't try to found one of my own if I plan on conquering my neighbors anyway) fealty may make sense, or if it looks like a domination aided culture or diplomacy victory is the best route then Artistry/Statecraft might be the obvious choice at that point.
Similar situation for the Industrial trees. Depending on how good or bad my conquering has been going, Imperialism might make sense or perhaps it will be time to pivot to Rationalism to get going on a science victory or Industry as a more all-purpose tree.
There are some interesting ideological policies for the Ottomans. In Freedom, the +2 trade route policy would be quite strong as well as Transnationalism ( Each turn, there is a chance that a Corporate Franchise will appear in a foreign city. Global franchise maximum increased by 20%.)- if I am unable to spread my corporation via trade routes for fear of them being pillaged and losing my completion bonus then having an alternative way for the franchises to be created could be nice.
In Order, Nationalization (Corporate Offices (up to your Global Franchise limit) function as Franchises. Foreign Franchises no longer benefit your Corporation.) could also solve the problem of having a tough time spreading franchises while Iron Curtain ( Free Courthouse upon city capture. +250% food or production from internal trade routes. City connections generate +5 Gold and Production.) could be nice if I am using a lot of internal trade routes.
Autocracy is overall just strong when domination is the goal but I don't see anything that synergizes with the Ottomans in particular.
--------------------------------------------
I'd be interested in hearing how others would play the Ottomans, or how they have played them in the past!