Well, interestingly enough I have been working on an article for people like me who are just trying to get their first WC. I should say that I haven't actually gotten mine yet, but I'm well on my way finally if my Ironman isn't broken by the Japan update. So I'm not really an expert, but these are the things I have found that have helped get me close. I would welcome comment from others who are more advanced than me. Let me know what you think.
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1) Before starting you should ask, Do I really want to do this? A good WC run can take dozens of hours over several weeks of playtime. In that same amount of time you could probably listen to a college course, learn the basics of a musical instrument, or watch all of Game of Thrones. I love EU4 so it’s worth it, but you should know what you’re getting in to.
2) DON’T PLAY TOO FAST! Before my successful WC run I usually played EU4 at speed 4, occasionally slowing to speed 3 for wars. Now I play at 3 almost always, and slow to 2 during major or multiple wars. There is just too much going on to play faster, and so some things will inevitably get missed.
3) The devil is in the details. Getting a WC or any of the other difficult achievements requires that you understand the details of many game systems. You must preserve your monarch points, especially administrative, so don’t ever throw them away. For example, if you get tech levels early it costs more. Weight the benefit of the early advance versus the savings of MP if you just wait a year or so. Similarly, you must be able to win wars even when you are weaker during the early and middle game; this is only possible if you pay close attention to army composition, bonuses, terrain, generals, etc.
4) Plan ahead – both strategically and tactically. First of all, plan your campaign. What are the major theaters that you will be focusing on, and in what order? You may have to do a few trial runs with your chosen country to see what issues you are likely to face in the first 50-100 years. Think about who your major opponents are going to be, and who might be useful allies against them. Think about where you need to expand to grow economically, whether it be accumulating rich lands or trading routes or both. Second, plan each war. While you cannot be completely at full strength for each war while doing a WC (it would take too long), you should have a reasonable plan to win each war. Plan where you will attack and, probably most important, be sure you know exactly who will be on each side. You should basically never declare war before spending some time really looking at the declaration screen and going back and forth looking at the strengths of each country that will be involved. Be SURE to pick the right casus belli; at least one of my WC runs was derailed at the end by going with the default incorrect one.
5) When you expand, your borders should not look natural. This is unsatisfying for those of us who are somewhat OCD, but you must get over it if you want a WC. There is no penalty for taking a strip of land right through your enemy in a peace deal as compared to the more natural (and historical) approach of taking a lot of bordering land. There are several advantages to this:
a. By snaking through your enemy’s territory, you can often get provinces adjoining new countries that you didn’t previously share a border with. This may open entirely new lands for conquest. For example, if playing as Russia or Austria you defeat the Ottomans, then you can snake through and get a border with the generally weaker Mamluks, which can then open all of Africa for a lot easier expansion than fighting the Ottomans over and over. Or snake through and get a border with the rich lands of Persia and then India.
b. You can take specific important provinces, especially those with trade bonuses and fortresses. One of the biggest impediments to a WC is sieging down the same damn forts over and over. During the peace deal take as many forts as possible; now they can be a pain in your enemy’s ass instead of yours during the next war. Also take provinces with trade bonuses; usually there are just 2-4 provinces in each trade zone with bonuses which will give you a majority of the trade power if you own them.
c. Sometimes you can cut off your enemy from the sea. If a country has no ports, it can have no navy. One of the most satisfying things I’ve ever done in EU4 is to take all of England’s coastal provinces in a peace deal and destroy a 100+ ship fleet instantaneously. Of course many of the trade provinces are on the coast as well.
d. By carving up your enemy into pieces, and then not allowing military access, you greatly weaken them against other countries and rebels. I have sometimes seen rebels take over an isolated piece of enemy land and create a new much weaker country.
e. Finally, if you isolate your enemies completely from each other and the sea, and again don’t allow military access, then they have nothing to do but sit there, develop their land, and accumulate money for you to eventually take from them. Think of it as fattening up the lamb before eating it.
6) Deficit spending. Think like the US government: If you’re not in debt, you’re doing it wrong. Money is the most liquid resource in the game, and you should probably have loans through much of the game. If you don’t then you may not be pushing hard enough, at least through the midgame. Don’t worry about loans at all (although certainly repay them when convenient) until you get more than 4-5 of them. You will frequently need to take loans to adopt institutions; it is almost always worth it.
