The Hanseatic Wars

Belligerents:
Outcome: The crowning of a French king as Holy Roman Empire; disintegration of any significant imperial authority.

One of the shortcuts that alternate-history writers take is using their plots to kill things that they're too lazy to research. While I'm endeavoring to not do this to ethnicities overly much, I'm not going to lie: I do it too. (And it's problematic for me because I have enough gaps in my knowledge of how things work that when I try to do this I still need to do all the research anyways.)

This is a related thing: using the plot to cleanly end a few crises ahead of schedule.

The wars commonly called "Hanseatic" (what they're called depends on which language and locale you're speaking in, because the politics of the matter are rather obscure) are the substitute for the Thirty Years' War: a crisis that plunges Germania into chaos. Unlike the Thirty Years' War, there are different demographic issues at work here.

And by the end of it, both the Hanse and the Reich have been crippled thoroughly enough to render them moribund.

The Hansa and the Güntherite cause

I haven't mentioned the Hansa very much yet, for a very simple reason: so much else is changing in the Holy Roman Empire that, while I'm reasonably sure it exists, I have no ideas what the exact details of its history are like prior to the early modern era. Barring any big changes in the history of economics (which alas I can't entirely rule out), though, it's going to evolve convergently enough, simply because it was able to evolve the way it did IRL for the good reason that it worked.

What this means is that by the time the Güntherite cause establishes itself, the Hansa as an institution is very likely losing out to the nascent nation-states, which are increasingly able to break its Baltic monopoly. As an economic institution, it's becoming a thing of the past, allowing for a different decline (so the Lübscher Adler, for instance, almost certainly never sails.) The Hansetag commands nothing like the power of the Reichstag (a fair number of Hanseatic towns don't even bother to send representatives, and don't consider Lübeck's decisions to be binding.) It's an institution relying heavily on its cultural capital: an institution of Low German merchant cities.

Fortuitously enough for it, one of the most importants of that century happens to be written by somebody from that demographic, in their language (more or less), for that audience.

Günther's Hanseatic ties, and the humiliating defeat that the Sansingers deal to the Emperor during the Baltic Wars, wins him a lot of recognition. It also helps that Lübeck is deeply religious (and stayed so even after converting to Lutheranism IRL, according to secondary sources), and gets won over shortly after Günther's death. The final flourishing of the Hanse also sees its transformation, from a foundering economic bloc to an emerging military-religious bloc akin to the Schmalkaldic League.

The trigger: the Great Ban

Something happens. Something like the incident at Donauwörth, but a lot less Swabian and a lot more Lower Saxon. Something in one of the Hanseatic cities. And a new emperor, heir to the one spanked in Pomerania, has been elected to office when it happens.

Under pressure from the Church (and possibly others? It's by no means unclear what families are in charge of what states by this point), the Emperor pulls out all the stops and bans the Hanseatic city in question. Legally it's dead; it has no rights, anybody can rob or kill it with no threat of punishment, and the Holy Roman Emperor gives any conquerors the right to strip the offender of their imperial immediacy. More importantly and seriously, anyone aiding to the city-state also falls under the ban.

The Hansa has to make a hard decision. It decides to take a hard line: Hanseatic power is collective. To abandon a city is to break the solidarity that holds it together, opening it up to death by inches and the doom of the Holy Church within the Empire.

Within a few months, dozens of cities have toed the Lübeck line. Across the Holy Roman Empire, large swathes of land - crossing the Empire's borders, in some cases, and including all-important cities like Hamburg, the Empire's beating financial heart - have openly defied the Imperial ban.

The fuse is set. All it takes is somebody to light a spark.

The explosion and after

Once the shit hits the fan, the major issues are as follows:

• The Holy Roman Emperor [who?], backed by the Pope and (nominally) Catholicism within the HRE.
• The Electorate of Saxony, [who?] the odd man out in this fight. (Saxony, as a High German state, stayed in the fold of Catholicism; with succession politics playing out as they do, however, the elector as of when the war starts is a reformist sympathizer. It's the only Catholic state to start and stay on the Hanseatic side of the fight.)
• The Electorate of Brandenburg, [who?] which is Güntherite, and opposed the current Emperor in election.
• The Hanseatic League, which is less a side than a battleground in the whole thing.
• The Swiss Confederation, whose fighting is going on at about the same time. (Of note here is that, unlike the rest of the Holy Roman Empire, the Swiss Confederation is partly Farrellite; this is the first war that the Farrellites take a serious part in, and their success here probably sets the stage for the unmitigated disaster that will become France.) Just as the Thirty Years' War gave rise to the independence of Switzerland, the Hanseatic Wars fill a somewhat similar niche (possibly moreso, if "Switzerland" includes any places that aren't part of it historically, like some parts of (say) Swabia or Romandy.)

In addition to this, there are a few other nations that might plausibly get involved:

• Güntherite Pomerania: Allied with Brandenburg and Saxony, and ready for another go if they can have their way;
• Denmark, which (irrespective of religion) has plenty of reasons to want Lübeck under its thumb, and which can be pulled into things via the Duchy of Holstein;
• Sweden, which may or may not be independent at this time (and may or may not have been dependent before);
• The Kingdom of France, whose crown prince may be in control of Imperial possessions, which would allow France to build an empire inside the Empire;
• The Turks, whoever they are, because the implosion of Central Europe is simply too good a possibility for them to pass up.

With this many players, forgive me if detailing the actual events of the Hanseatic Wars are, and remain for quite some time, a work in progress.

The aftermath of the Hanseatic Wars

In the aftermath of the Hanseatic Wars, the Holy Roman Empire becomes vicarious.

• At the council, several of the German princes take the opportunity to declare themselves kings. (Oddly enough, the Elector of Saxony [who?] doesn't, and styles himself an archduke instead. When asked why, it's because he'd rather be first among dukes than last among kings.)

It bears noting that while the Holy Roman Empire is moribund, it isn't dead. While there hasn't been a meaningful Holy Roman Emperor in centuries, the institutions of the Empire are still in place; for that matter, without a legitimate Emperor, Switzerland and the Low Countries don't have a precise need to establish themselves as independent states.