Dainam War - Royal Ordained Medal of Ngan Bai Bar (Nghi Hoa-Cong/Sac-Tu)
Dai Nam starts off the most powerful nation in its area, with only Siam (and obviously China) coming close to it in power. At the outset, China has no interest in interfering with Vietnam, and neither do any colonial powers leaving the player to work towards westernization and gobbling up neighbors with relatively little interference. Also, you have two tropical timber provinces, which, due to the terrible price of tropical wood, rapidly become soldier provinces. You will find yourself able to recruit more than 10 brigades from one province by the 1840s. You also have a small satellite, Cambodia, that will loyally send a few regiments to fight in whatever wars you might get in.
However Dai Nam has many disadvantages. One of these is that, while it is big for the area, the starting population of around 1.5M will not grow without modifiers, due to the life rating. This means you will be stuck with 1 Focus Point for most of the game. Your population is incredibly illiterate, slowing research and making it hard to promote (even to clergy), and of course, being uncivilized is a major downside, with your technological situation in shambles. With almost no literacy and an uncivilzed label, almost all your research comes from clergy. At the outset, your military will be all irregulars and you will be unable to recruit infantry for several years, until the world market catches up with the demand for small arms.
Always remember your main goal is to westernize, and to do that, you will have to wait for tech while also earning 40 prestige and a military score of 50. You can't do much to accelerate the tech, except by gaining literacy or clergy. So you need to make sure the other two are ready when the day comes. More on that later. Do not research techs that are not necessary for westernization
Before unpausing, move all budget sliders all the way to the right. While it's permissible to skimp in a few areas, like administration and possibly military, education is not one of them. With terrible tax and administration efficiency and an equally poor tax base, you will need every penny, so full tariffs and taxes are called for. Remember that at your level of tax efficiency, even all the way to the right you aren't collecting much tax. Also bear in mind that every extra brigade helps your military score requirement for westernization. Keep the military spending as high as you can bear; every brigade counts towards the military for westernization.
Research Freedom of trade first. It's required for westernization, and the production bonuses will make your budget situation much nicer. You will be supporting a much larger force soon.
Set your national focus to clergy on either your northernmost state or the middle one. The middle one starts with a higher population, but they tend to migrate north.
You may also want to consider recruiting artillery, which is easier to find on the world market than small arms at this point. Artillery is a very useful complement to irregulars, which you may want to also build. Naval building depends on your strategy.
If you plan on attacking Siam (see next section) an alliance with Johore will serve you well. Otherwise, it is going to be a liability; Johore tends to get attacked by the Dutch, a war you will probably try to avoid at the cost of some prestige if you are allied. Other alliances are at best useless. Keeping several nations unallied is a good idea so you can build up prestige with humiliate wars as you need to.
Picking a target
For the warmonger, there are three nations you can set your sights on - Korea, Japan, and Siam. Each of these offers multiple states for you to take. Attacking China would be foolish, and any other country (like Luang Prabang or Johore) would require you to use a conquest wargoal - and 20 infamy. Of course, they are good to humiliate for prestige, and humiliating Luang Prabang is a good day-1 warmup. In the long term, to grow, you need to attack one of those three.
Of the three nations, Siam is the closest; invading it requires no boats. It has 6 states so your first war is probably going to require the "free people" wargoal on a couple of them so you can use "conquer" in the second war. Siam makes a nice feather in your cap, but also gets you a land border with the United Kingdom, which is a recipe for trouble (or a constant drain on diplomacy points to keep yourself in their good graces). Siam is also a good exercise in jungle warfare and the war is not that hard. Send stacks of 2 brigades to seige, but keep your main force just behind it in your own territory. When they attack, plow in your main force. They will probably have -2 from terrain and -1 from a river crossing, making them a few big slaughters away from defeat. Don't be afraid to get an alliance with Johore before you try it; the distraction of Johore will keep Siam from building a big force and make the war fairly easy for an alert, skilled player.
Korea is a greater challenge. On the upside, it can be conquered immediately with the conquest wargoal because it is only 4 states and provides useful industrial goods. It has a much greater population than Siam (or, indeed, Dai Nam) as well, and is located with a life rating that is friendly towards growth. You will need a lot of ships; my attempts to invade with only 6 brigades ended in failure. The trick here is to land your force in the north where you can use defensive terrain to your advantage - and get a lucky roll in the first battle. You will want to keep your forces close to each other so they can rapidly reinforce whichever stack gets attacked. Hopefully, you can wipe out a korean stack and get time to bring additional reinforcements. The same basic strategy as Siam applies, where you draw them into a defensive battle and reinforce. Don't be afraid to hunt down a defeated stack, but be very wary of attrition.
The third choice is Japan, and that's the one you want to attack. You can get the most valuable province for thousands of miles without a land battle.
Osaka Region: The Crown Jewel Of the East
This one region is everything you could ask for. The pops are numerous (at around 2M, more than your whole nation!), and relatively literate (around 40%). The literacy is a game changer - in a game where I took Osaka, I got the tech to westernize in January, 1848 - when I took Siam and Korea, both led to westernization in 1856. It has a precious metals province that will crank out the money. Because of the size of the population and its literacy, not only is your average literacy boosted, but your national focus is much better used on it - pops promote to clergy much faster, and you will be able to cover more than half of your population with one national focus. As if all that weren't enough, Japan values this province lower than the most obvious one you'd want to take, Fukuoka (which covers the Southern Island, Kyushu).
Fighting a land war with Japan, though, is almost impossible; the Japanese will have far more soldiers than you can muster at this point. You might have additional artillery, but that's of little consequence. If you wait more than a year or so to build up, China will become Japan's ally, making the war a doomed effort. But, if you plan correctly, you will have naval superiority, which will be the key to the war. Don't forget to declare war around the start of 1837; you need to do so before they ally with China, even if you aren't ready.
Your initial naval squadron should be a good number of clipper transports (say 10), and hopefully a handful of frigates. The Japanese will only have clipper transports, and not 10 certainly. A few frigates will easily establish naval superiority, but transports will do if that's all you have, at least at the outset.
Move to the Setto Inland sea with several small armies in your holds, then declare war. With any luck, the Japanese armies will all be on the large island, Honshu. disembark your armies on to the two other main islands, Shikoku and Kyushu. Hold the setto inland sea province with your transports - they will be taking attrition, but soon a captured province will put an end to that. Rotate them back to Dai Nam for additional troops or to reduce attrition. Or hold that sea province with frigates.
Do the same with the northernmost island, Hokkaido - land while the straight is blocked, and keep it blocked for the whole war. When you get the chance, land a brigade on Okinawa and Amari, the small southern island provinces.
Whatever you do, do not lose control of those naval provinces. Pile in every transport you have if you have to, don't be afraid to lose a few. Don't forget you can disembark from transports while in combat. You can take each province with only one brigade, you can spread them out fully to minimize the time you have to spend.
Once Shikoku, Kyushu, Hokkaido, and the minor islands are fully in your control, you may want to split up your navy some to enforce a blockade on the other parts of the Japanese coast. Make sure to duck any such blockade ship into a harbor before you send it to blockade, to reduce attrition.
All together, this will give you enough warscore to get Japan to give you Osaka without any land battles. If you are feeling adventurous, assemble your forces near one of the straights and invite the Japanese to try and cross it. As soon as they do, they will get a -2 crossing penalty, and you can move your ships in to prevent them from getting support. This is unnecessary, though.
With Osaka captured, put your clergy focus on it; as previously mentioned it will be much more effective here, even though these pops are already far more literate.
Build artillery and irregulars as much as you can. Build additional ships as well. It can be a balancing act, because artillery will be recruiting very slow as necessary inputs (like liquor and wine) are hard to come by. Don't leave a province with many brigades unrecruited, waiting on artillery, if you can avoid it. If you are going to war with Japan again before civilizing, you will need these.
Whether or not you war with Japan again is mostly dependent on Japan's alliance with China. The UK has a so-so chance of declaring war on China, which will break the alliance. If it does not, you are building armies and ships (don't be afraid to build men of war) for the sole purpose of military score for westernization. You will need to start humiliating neighbors like Luang Prabang, Johore, Brunei, etc to get your 40 prestige. In my game the Japanese-Chinese alliance broke down and 5 years later it was time for war.
Your second tech should be napoleonic thought in preparation for that second war. If you don't see it happening, get private banks instead; that will give you a little more tax money to play with. All throughout this period you will be trying to juggle the financial demands of a huge military and navy with your economic backwardness, so that 3% can help. You shouldn't need massive tariffs after taking Osaka, but the extra soldiers will need to be paid as well, and the steady supply of clipper convoys and artillery you'll need are not free.
The Second War
The second war is far more challenging than the first - you need to hold your ground against a huge Japanese horde. To begin with, you can't keep anything like the size of their force on the islands, due to attrition. It's actually a good idea to put 30k soldiers or so on boats on the setto inland sea (hopefully they've moved some troops to shikoku or kyushu - troops you can now keep out of the battle). Ironically troops on boats don't suffer attrition, so they make a good parking place for reinforcements.
Your best target is probably Nagoya, to keep your borders less complex, but the choice is much less clear this time. You probably should leave some of the smaller islands to the Japanese, so that you can bottle them up there in any future wars.
You will need every trick in the book to beat the Japanese. Shuffle your defensive generals to whichever stack they are attacking (stay on the defensive at first). Try to get encirclements when you can; I had a couple battles where the Japanese retreated to Nara, where they were encircled. Retreat low-org units from the battle and cycle in new ones. Keep building artillery and irregulars and keep bringing them to the front - ignore Dai Nam entirely (you don't need any soldiers there). I also found that buying wool manually on the market kept my irregulars regaining org - why this did not occur correctly automatically, I don't know, but pay attention to org regain as well. Pay a lot of attention to attrition, especially in your own territory - keep units spread out to avoid it. Pay attention to when the month is ending and keep units with few soldiers but lots of brigades in position to receive reinforcements.
This war will require a lot of tricks and deep understanding of the nuances of the combat system. It's not easy. Don't be afraid to send damaged and recovering units to any smaller unoccupied islands; also don't be afraid to blockade the Japanese. Raising their warscore will help you out. If you are lucky and good, with your defensive bonuses from post-napoleonic thought, a few good generals, a lucky encirclement or two, a lot of artillery, and units trapped on smaller islands will lead to your victory. Once you have dispatched the forces on Honshu, you can conquer as you would like. Depending on your infamy, you may want to take a second state, depending on how much infamy.
Of course other states are a double edged sword; they will be an industrial boon when you are civilized, but they cost far more infamy now (10) then they will as colonial concessions(4), and they water down the effectiveness of the NF somewhat.
The good news is that the huge battles will be a boon for prestige; I gained around 25 in the course of the war. No more humiliations will be necessary, so you can keep some infamy for the post-civilizing period.
This war is rather optional, but given the size of the Japanese horde and that you will not be getting military techs for a while, it is probably good to at least weaken them somewhat. Obviously if allied with China, this is not an option
Regardless of who you went to war with - Siam, Korea, or Japan - or how many times you did it, you need to westernize. 40 prestige is achieved by as many humiliations of minor powers as you need to undertake after conquering. 50 military is trickier. Keep a clergy national focus on your most populous province; they not only boost literacy but are the main component of your research at this point in the game as well Officers contribute a lot, but their deaths are not something you can control. Make sure that auto-create is on so you don't forget and hope that they live. Don't use an officer NF; it's too ineffective. Instead keep your military spending full so soldiers can promote.
Build as many brigades as you can, and keep them as well equipped as you can. It's useful to keep a province training an infantry; when you see that it has started building then you know small arms are on the market. Disband irregulars in favor of infantry as fast as you can. Build ships as well; men of war are the best for this. Remember you don't need to fully fund your national stockpile (or fund it at all) in order to get military points, so keep cranking them out as fast as the clipper and artillery markets allow. (Of course, at very low national stockpile settings, you will never get enough to build the units - don't set it that low).
Switch to the nationalist government; the extra supply cost of jingoism will boost your military score.
When the time of westernization is close (check your tech progress), start a humilate war against Luang Prabang or a similar nation. Sweep in, get to 100% warscore, and wait until the tech is done. The day it is, pause and offer peace; they will be compelled to accept. You will notice the decision option light up immediately - do it immediately. Failure to do it will cause the extra military score you got from the at-war supply demands of your forces to dissipate, which might plunge you below 50 military.
If you went the Japan route, you will be westernizing in the late 1840s and will instantly be a secondary power. Research idealism, a tech that boosts your research considerably. Set up your factories how you like, and ponder your next moves.
There's a lot to do in this phase of the game, and many tricks will need to be employed. You'll want to take as much of Asia as you can before foreign powers gobble it up; you'll want to reach great power status so you can take nations like Korea in one go (with nationalism and imperialism) and so you can duel with the other powers for influence in these areas. You'll want to establish naval bases to be ready for colonization, and maybe got on a colonial expedition to the east to be ready for the scramble for Africa. You'll want to do what you can to boost your vietnamese POPs - which may mean a liberal government to encourage assimilation, and/or socialist health care policies.
Your ultimate goal is up to you. I'm a natural warmonger, so my goal is always world conquest, or something like it. You could limit your ambitions to asia and try to establish a co-prosperity sphere of your own, or try and kick the British out of the area. Or maybe your Place in the Sun lies in Europe! With Japanese and Chinese soldiers fighting under your civilized banner, anything is possible. The major powers won't take your growth lying down and the British hordes in India will come for you eventually. Will you be ready?