So I'm playing England as a Cromwellian American conquest run (basically take over all the Americas and try to buddy up with the Dutch to help them take over everything else) when I joined the Protestant League out of shits and giggles, as I noticed the Protestant League was so underpowered they were pretty much doomed to failure unless I joined (being led by an Orthodox greek OPM versus Austria, the Papacy, Serbia, all Knight orders, Poland, Lithuania, Muscovy, the Hansa, most of the German petty states, France, Naples, Tuscany and Denmark to name the big guys. On the protestant side was Saxony, Sweden, Scotland, Norway, the Kazan horde and the Timurid horde. Eh... Ok then.
So I joined the league and after warring with the Spanish over the Caribbean some more I left the league, then rejoined when I found out Spain had entered the protestant league. Whilst gauging the strength of the leagues I accidentally declared war on the Austrians and started the world war, and I couldn't have been luckier. Well, I was hoping the Ottomans would've joined the league but they were stuck with the Mamluks and Timurids. I was lucky because the French had declared war on Austria... On the Papacy's behalf! The French began cleaning up the Austrian stacks and the English helped them win some early battles, but after time I noticed disparagingly that all the soldiers of the new world were not going to be of much help in the old world. I knocked Denmark out of the war but then the grand slavic army from Poland to Muscovy and everything Lithuanian in between just utterly swamped Norway and Sweden, and right as I pushed back the Austrian ubermensch and was about to take Vienna the slavs attacked.
Several times I lost everything, with my troops slaughtered by the Russians when I nearly took Vilna and knocked Lithuania out of the war, slaughtered by the SlavoAustrians when I nearly took Vienna, slaughtered by the Venetians when their fleet surprised my heavies (my navy was used to ruling the open seas... The Mediterranean belonged to Venetian galleys), eventually it got to the point where English gold and Spanish troops were the only thing keeping the Protestant league from descending into total collapse.
With Venetians destroying my transport fleet and the Anglo-Spaniard army having routed the pan-Slavic army, the English pursued them to inflict a 40,000 man dent in the coalition of 400,000 soldiers. Not to be balked at, as this was a global war. The entire army would've been crushed was it not for the action of one particularly resilient unit of Hussars that somehow defied my entire army for two weeks before being killed to the last man. I lost 100 troops, they lost 500 - they should have lost all 40,000! Those Hussars bought enough time for the German-Italian forces to arrive and Venetian galleys to destroy my transport fleet. I had to start from square one again.
Towards the 20th year of the war the Royal Navy had managed to gain access to the ports of Achaea, the Greek Orthodox OPM that started it all. From this port the Navy began completely blockading Lithuania, Aragon, Naples and Austria - knocking them out one by one with Sicily becoming the de facto English mercenary training camp. From Calabria and Salento and the hills beyond the English troops waited and as the Spanish had been knocked out of the war (not before fighting a brutal series of battles in France funded by English gold whilst English troops killed all the troops sieging Spain herself), the English troops in Naples were the last thing in all the world stopping Austria from forcing Catholic victory. Amusingly Scotland was the last ally in the league to leave the war, leaving just 1 year before the end. The Catholic league sent everything, but by then were so exhausted that all the German princes grew tired of having their troops wasted on the English troops who had avoided having their homelands affected by blockade or siege. Most amusingly I managed to reach peace with the Polish Lithuanian Muscovite forces right before they reached Calabria, having marched all the way south they saw my 45,000 well-supplied men and just said 'fuck it, let's go home.' With just one correct invasion (and a total blockade with 20 years of warfare) the English defeated an army ten times its size, gave the Papacy control of much of Naples' lands (as a thank you for taking France out of the war) and then lay siege to Austria herself. I was finally about to take Vienna after 20 years of war and secure protestant victory, to give Saxony a little help.
Then the Dutch declared independence and brought me into war with France and her friends. 20 years of warfare was undone in one week. I signed the peace of Westphalia.
Aaaaaaaaaaaaaaaaaahhhhhh
At least Achaea is my friend now
*EDIT
Austria was fighting all of these countries at the same time and managed to stalemate them. Dayum.