Long time lurker, but first time post.
Figured I'd share my empire after getting the Poland into space Ironman achievement. ^___^
I decided not to get into a personal union with Lithuania at the start in order to simplify the westernisation process: I wanted as little territory as possibly to avoid having to deal with a large scale civil war and also wanted to minimise building in weak provinces and focus on reaching max tech. In hindsight I could have just kept them in a permanent PU, but Lithuania tends to barely be able to handle its own internal strife (notice the large Polotsk and Ukraine acting as a nice buffer between Russia and myself), let alone assisting someone else. Basically it's best to ditch Lithuania the moment they start raking up large War Exhaustion. Therefore I allied with Austria and Lithuania, and started coring all of Hungary's provinces within the Krakow centre-of-trade (which allow you to maintain a monopoly while also providing a nice buffer between the Ottoman Empire and yourself; it also wastes a lot of the OE's administration power (because of Hungary's +200% coring penalty) hindering their expansion by a decade or so). After having acquired the territory around Pest, I became strong enough to diplo-vassalise+annex Masovia (which gives a nice event), Pommernia and Mecklemburg. Around that point, I cancelled my vassalisation with Moldova after acquiring a land border with the Ottoman Empire. As anticipated, Moldova got annexed shortly afterwards. I was very lucky westernising, having seriously underestimated the difficulty of westernising comapared to that of EU3. The systematic hits to your mil and dip power effectively paralyse you tech-wise. Ironically, westernising caused me to fall behind . Luckily for me, I had a high admin monarch at the time (a BIG must for anyone attempting Westernisation) allowing me to escape the rebellions of Westernisation. While I was lucky enough not to get attacked during westernisation, my ally Lithuania crumbled during my period of westernisation, unable to handle the WE it gained following its victories in Moscovy. Ironically, all the cores it had gained defected back to Moscovy and Ukraine and Polotsk declared independence. Lithuania was shortly gobbled up by its own progeny. However, immediately after successfully westernising, the OE decided to show me who was boss with its ally Crimea. They proceeded to thoroughly rip me a new hole (despite me attempting to immediately peace out at the start of the war offering +150% War Score worth of provinces), deciding that if they wouldn't give me peace, they could simply take what they liked and I could minimise my WE. Surprisingly, the peace they ended up suggesting was a lot more generous than the one I had offered them: asking me to release Krakow and Masovia as well as giving them all my Hungarian cores). The huge WE and manpower losses I acquired from deliberately letting the OE invade my territory paralysed me for another 20 years. I then sought a new alliance: France, the most hated nation in West Europe was desperate for allies. I wouldn't recommend doing this if the Emperor is strong, but in my game Austria was getting beaten on quite hard, and ended up losing the HRE title to Bohemia (the entirety of the HRE defected to the protestant faith, leaving Austria on its own, and would even go on to forming the HRE in the mid 1700s). In fact, by securing Pommern and Mecklemburg in the early game, it prevented any northern powerhouses from developing. (leaving Denmark and the Hansa with few areas to expand). Bohemia did try declaring war on me (due to their rivalry), but lost Silesia in the process (remember to always fabricate claims on EVERY bordering province; just in case you need to use them); after that they were too weak to achieve anything in or out the HRE (luckily though they had inherited a war-free HRE.
The map as you see it has been virtually unchanged over the last 100 years. Most of the wars were between the Spain+HRE+England Coalition vs France (usually resulting in the exchange of some minor colonial provinces) and the Sweden+Crimea vs Russia coalition for some worthless provinces. After having achieved the world's largest military force around the mid 1600s and having avoided any expansion-related negative opinion modifiers (the only state in the region that couldn't stand me was the Ottoman Empire) regional hegemony was reached. Finally, the Liberté, égalité, fraternité and a lucky 6/6/6 monarch towards the end helped me reach my goal well ahead of time.
To anyone attempting the achievement: Firstly, you don't need to westernise. Westernisation really screwed up my Poland bigtime. I was REALLY lucky that during the westernisation process, no one declared war on me: I doubt many players will be so lucky. Furthermore, I lost several levels of tech from my nearest neighbours (though I caught up a century later, and the boost helped me maintain a 1 military level lead over the Eastern tech group at all times). If you DO want to Westernise, a tip is to grab a diplomatic NI and dump all your diplomatic power into that NI; thereby giving you some benefits as well as Poland's unique NIs. You want to deliberately let your Diplo tech fall behind, like that you can westernise faster. (you need to be behind by a total of 8 levels from all your techs combined). You can stop adding points in admin once you've picked up the constables+temples tech. On the other hand, don't let your military tech fall behind! While it may sound tempting, without a high military tech, I'd never had made it through Westernisation (those rebels really hurt; I think it might have something to do with me switching from and inferior military group, and therefore they acquired the more advanced western techs). Make the most of your pre-westernisation time to build constables and temples everywhere (you'll need good income to maintain a strong army during the Westernisation process).
Another tip which I can proffer in hindsight, is not to take the "move your capital to Warsaw" decision until after you westernise (as the event itself gives 3 stability). Seriously, getting above 0 stability after westernising is a PAIN.
Tips for defeating the OE: Muscovy, and to a lesser extent, France and Spain are your friends here. Muscowy's winter attrition wrecks the armies of Crimea and the OE, while at the same they do a good job defeating them on land. The higher you can bring up their WE, the more likely the OE is to peace out.
TL;DR: Poland is really fun! I've usually avoided playing Poland given the poverty of the region in previous EU games, but I'm glad that the achievement baited me into playing a game as Poland.
It's a really challenging region wedged between the HRE, mighty Russia, and the OE. Luckily the HRE and Russia hate the OE enough to ignore you. <3
