Been playing Hearts of Iron 2 the past few weeks, just finished up a campaign. It's a WW2 "What if?" game, set before, during and after. And you can play as almost any nation present at the time.
I decided to try and save Poland by attacking Germany preemptively in 1937. I first blitzed Czechoslovakia to have a better position to attack, and with great effort (lots of close calls) I managed to beat Germany.
Then I decided to attack Austria, Hungary, Yugoslavia and other smaller states to see when someone will get angry and stop me. The first to declare war on me was Turkey.
The Allies declared war on Turkey because they guaranteed my independence (although I wasn't in the Allies). The Soviet Union declared war on the Allies because they guaranteed the independence of Turkey. The alternative World War 2 was in the Middle East, between Soviets and Allies. Japan declared war on both sides after a while, doing a land grab of Allied colonial possessions and eastern Russia. The US joined the Allies and took the fight to Japan.
It was a nine year long WW1 style brutal stalemate on every front. Meanwhile Poland who started it all wasn't even involved in the war - we weren't part of any alliance and we were only at war with Turkey which was split between the Soviets and Allies within months of the war starting. So Poland just sat back and built up its military and industry.
tl;dr Poland conquered the entire world by 1952, the last to fall was Argentina.
I challenge your Hearts of Iron 2 with my Europa Universalis 3, behold!
http://i.imgur.com/wNkyBrE.png (the world is already mine, just click on that decision, and POOF! I inherit everything from my vassals!)
It was pretty intense, starting in 1399 as an Ottoman vassal, heck, I still remember ruining my economy just by conquering Montenegro, Albania, Transylvania, and Wallachia by hiring lots of mercenaries. Thankfully the Timurids managed to take half of the Ottomans' territories at Asia Minor, so I seized the opportunity and conquered Constantinople while the Ottomans were at their weakest.
Hundred years have passed, and I somehow managed to get Burgundy (who would then "reincarnate" as France) to be my junior in a personal union, and then I started my grand campaign of global domination and faith unification. From a humble beginning as a lowly vassal with a yearly income of 56 ducats, now I can just send a horde of 100000 Napoleonic Square stacks around the world and I can still get a yearly income of 5000 ducats.
(P.S. : Please come back Joe.)