By Alex Richards
By 1623 it appeared to many in Europe that the conflict in the Holy Roman Empire was over. Frederick V of the Palatinate and his family were in exile in the United Provinces, the majority of his supporters either joining him or reconciled to the Emperor. And yet the Peace of Westphalia was still 25 years into the future, and many of the conflicts most famous- and infamous- moments were yet to come. The key to understanding this, and the escalation of the conflict to incorporate more of Europe, lies in the subject of today's article: The Danish Phase of the War.
The Danish War began in 1625 when an alliance of Northern Protestant realms- Denmark, the United Provinces and England- came together with the aim of securing the Lutheran states of northern Germany against the potential predations of the now triumphant Emperor. Backed by French monetary subsidies, King Christian IV of Denmark assembled an army of 14,000 and moved into the Principality of Lüneburg (also known as Celle, Brunswick-Celle or Brunswick and Lüneburg) in an attempt to get more troops from the states of the Lower Saxon Circle of the Holy Roman Empire. In addition, Christian desired the Prince-Bishoprics of Verden, Osnabrück and Halberstadt (all at this time run by Lutheran administrators rather than Catholic bishoprics) for his younger sons.
In response, Albrecht von Wallenstein, freshly enriched with confiscated territories in northern Bohemia, sought and gained permission to raise an army of 24,000, reinforced to 50,000 from other parts of the Empire. Meanwhile the 25,000-strong army of the Catholic League (a Bavarian-led anti-Lutheran alliance) had moved north into Lower Saxony under Count Tilly as a result of his military actions against Mansfeld and Charles of Brunswick. The two armies dealt a series of comprehensive defeats to the Protestant armies eventually leading to Wallenstein occupying the whole of the Jutland peninsula. Unable to acquire a navy sufficient to force passage to the islands and Copenhagen however, a lengthy stalemate ensued and Denmark sued for peace in 1629, agreeing to withdraw from Imperial affairs in return for the return of all her occupied territories without territorial loss.
Could Peace have Prevailed?
The most obvious question from all this is whether a longer-lasting peace could have prevailed after the end of the Palatinate phase of the war in 1623. There were two key factors leading into the Danish phase of the war, both of which can be considered consequences of the Bohemian Revolt and serve to bridge the two conflicts together over the intervening years of peace.
Firstly, and the reason which was to be used as an excuse for intervention many times of the next couple of decades, there was the matter of Frederick V's claims to the Electoral Palatinate. While technically all lands and titles within the boundaries of the Empire were held by gift of the Emperor, this had become a mere formality centuries before the Thirty Years War and the principles of hereditary succession held sway. While Frederick had been placed under the Imperial Ban, giving the Emperor the right to revoke his titles, transferring the Electoral lands and title to Bavaria at a stroke represented the single biggest shift in Imperial power dynamics since the Peace of Augsburg. When combined with the smaller changes in Baden and the wholesale dismantling of the Bohemian nobility, the perception for many in the Empire was that Ferdinand III wanted to reorganise the entire Empire to better suit his preferences. In these circumstances the restoration of the Palatinate, either in whole or in part, usually with the Electoral Dignity as well, became a rallying cry against Imperial power even by those who didn't particularly like Frederick V.
As I've outlined before, considering Frederick's personality the only realistic way to achieve a resolution of the Palatinate issue is the exiled erstwhile Elector dying much earlier than historically. It would still be politically difficult for Ferdinand to restore even the lower Palatinate considering by 1623 he had confirmed Bavarian ownership of the territory, but it remains potentially possible even at this stage if Henry Frederick (or his appointed regent) is willing and able to make a suitable homage to the Emperor. It is likely at this stage that such an act would be without any form of Electoral title unlike the historic results of the Treaty of Westphalia.
In many ways the Palatine was merely an excuse however. The Bohemian Revolt in itself might have been able to remain merely a Habsburg domestic matter. Frederick having an uncharacteristic bout of humility, or more likely a sudden death, in the 1619-21 period might have prevented a greater escalation, but the utter dismantling of the foremost Calvinist power in the Empire came hand-in-hand with the dissolution of the Protestant Union, the alliance of Protestant states which the Palatinate nominally headed and which had offered weak protests before Ferdinand had ordered its army to disband.
Clear favouritism towards the Catholic League- it having always been Imperial policy beforehand that both the Union and the League were unnecessary and should be dissolved and an emperor willing to make drastic changes to the status quo meant that there was a great deal of agitation towards a reassessment of the balance established by the Peace of Augsburg largely focused around the fate of church properties secularised (either de jure or de facto) in the years since by the northern Protestant princes. While these causes historically played more into the events of the Swedish Phase of the war, any delay to the Danish phase simply makes it more likely that Denmark will intervene for similar reasons.
In the middle of this were Christian IV's own ambitions. Having inherited the Imperial Duchy of Holstein, he had successfully enforced his overlordship of Hamburg and was seeking to push his influence south beyond the Elbe to become a major player in northern Germany in his own right. Conflict with Sweden, domestic issues or especially a lack of French subsidy might lead him to reconsider his intervention in 1625, but these ambitions are unlikely to go away, and in the absence of the defeats of the historic campaign we could easily see Denmark enter into the conflict later than historically for much the same reasons.
There remains one very interesting possibility. In the months leading up to the Danish invasion, Gustavus Adolphus of Sweden had expressed an interest in intervening for the Protestant cause. However, with Sweden still busy conquering Livonia from the Polish-Lithuanian Commonwealth, the Swedish offer required 20,000 more soldiers to be raised by the states of Northern Germany than Denmark's already modest request for 30,000 soldiers. As such, Denmark took the initiative, but had Sweden been less demanding, or Denmark more so, it would have been quite possible for the Danish Phase to be essentially skipped altogether resulting in an earlier Swedish phase of the war. And with Gustavus Adolphus entering the War earlier than historically, a significant overturning of the historical wartime situation may well be on the cards.
 The Circles of the Empire are worthy of an article in and of themselves but basically served as a regional councils primarily focussed on dispute resolution and military co-ordination.
Alex Richards is the author of Tippecanoe and Wallace Too, published by SLP