And you are considering THIS a challenge? "It is elementary, Watson!"
Mathias is a Hapsburg so him being a die-hard Catholic is natural. And, unless a ruler manages to create a special institution to dealing with the nuisances of the multiple religions (which was a thing done only in the XVIII - XIX centuries), of course he wants an uniformity. Can you imagine a headache caused by the need to resolve quarrels of all these religious lunatics? And, let's face it, nothing personal but these Calvinists were really obnoxious. Of course, Matthias wanted to deal with Protestant heresy but the problem was in him not having enough money to raise and maintain a decent army. The money had to come from Bohemia but the bohemians (being by definition people "having informal and unconventional social habits") refused to grant him money for their own suppression, which was "unconventional", to put it mildly. The Catholic League had one but it was listening to the orders of Max of Bavaria. The Spanish cousins promised to provide some military help from the Spanish Netherlands but was just enough to deal with the rebels in Bohemia.
As for GA, well, he was a Vasa and, judging by Sigismund & Co, they were ardent Catholics as well. Split between Sweden and Poland had nothing to do with religion (as everybody knows, Sweden remained a bastion of Catholicism in Scandinavia), just with the obvious inconveniences of having and absentee king who was also suffering from the unhealthy ideas regarding establishing an absolute monarchy.
GA timely came with a proposal to provide Mathias with an army which he is going to maintain at the expense of the rebellious German princes (
bellum se ipsum alet) and Matthias jumped to the opportunity. Of course, Swedish army of GA was quite small but he already got a reputation of a successful and
generous leader in a war with Lithuania (1617-18) in which, except for Riga, the whole Livonia had been thoroughly looted with a loss of up to 80% of its population. Small wonder that he did not have any problems with raising size of his army to 50,000 and then to almost 100,000 within couple months of his landing in Pomerania. The ailing Mathias made him generalissimo of the imperial armies and "
Admiral of the
North and
Baltic Seas' and gave him the Duchies of Meklenburg (both dukes were protestants, did not mend their ways in a timely fashion and had been places under the imperial ban). Mathias died in 1619 and operations continued during the reign of his successor, Ferdinand II, who granted GA the Duchy of Pomerania in addition to Meklenburg. By the time GA occupied and annexed the whole Brandenburg, his army was too big for Ferdinand's objections to be practical. His acquisition of the Duchy of Prussia was not the imperial affair at all. As every decent student knows, this was a beginning of the German-Swedish unification which ended at some point in the XIX century and as such is not a subject of the essay (too much knowledge can be hurtful).
Do I have to add something about the bear-riding Muscovites coming to GA's help in the most critical moment or would this be out of the essay's scope?
Well, how about the Polish winged hussars (you can't get wrong with them) helping GA to defeat the Ottoman-Brandenburg army besieging Vienna?
Of course, Richelieu was trying to undermine the Hapsburgs by subsidizing Protestant rebellions in Austria and Spain, which prolonged conflict which ended up being known as "2 and a half Years War". While the fighting was going on, Richelieu quietly annexed Princedom of Monaco and made it a center of the international gambling business (and the main source of income for the French crown).
That's simple. After facing a severe financial crisis (which was a typical situation for the Austrian branch), he reassessed his priorities and issued an edict saying that the only heresy in his domains is not paying taxes in time. (*) By that time all Protestants in Bohemia are killed so no substantial contradiction with all of the above.
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(*) An idea is borrowed from the cycle "Adventures of John, Duke of Meklenburg" by Ivan Ochenkov (with Meklenburg being changed to the Hapsubrg's territories)
