The Swedish invasion of Brandenburg (1674–75) () involved the occupation of the undefended Margraviate of Brandenburg by a Swedish army launched from Swedish Pomerania during the period 26 December 1674 to the end of June 1675. The Swedish invasion sparked the Swedish-Brandenburg War that, following further declarations of war by European powers allied with Brandenburg, expanded into a North European conflict that did not end until 1679.

The trigger for the Swedish invasion was the participation of a 20,000 strong Brandenburg Army in the Holy Roman Empire's war on France as part of the Franco-Dutch War. As a result, Sweden, a traditional ally of France, occupied the militarily unprotected margraviate with the declared aim of forcing the Elector of Brandenburg, Frederick William, to sue for peace with France. In early June 1675 the Elector and his 15,000 strong army decamped at Schweinfurt in Franconia, now southern Germany, and reached the city of Magdeburg on . Frederick William, led the campaign against a Swedish force of between 11,000 and 12,000 men. After one week the Swedish troops had retreated from the Margraviate of Brandenburg.

Background After the War of Devolution, Louis XIV, King of France, pressed for retribution against the States-General. He initiated diplomatic activities with the aim of isolating Holland completely. To that end, on 24 April 1672 in Stockholm, France concluded a secret treaty with Sweden that bound the Scandinavian power to contribute 16,000 troops against any German state that gave military support to the Republic of Holland.

Immediately thereafter, in June 1672, Louis XIV invaded the States-General - thus sparking the Franco-Dutch War - and advanced to just short of Amsterdam. The Elector of Brandenburg, in accordance with treaty provisions, supported the Dutch in the fight against France with 20,000 men in August 1672. In December 1673, Brandenburg-Prussia and Sweden concluded a ten-year defensive alliance. However, both sides reserved freedom to choose their alliances in the event of war. Because of his defensive alliance with Sweden, during the period that followed the Elector of Brandenburg did not expect Sweden to enter the war on the French side. And despite the separate Treaty of Vossem agreed between Brandenburg and France on 16 June 1673, Brandenburg rejoined the war against France in the following year, when the emperor of the Holy Roman Empire declared an imperial war (Reichskrieg) against France in May 1674.

On 23 August 1674, therefore, a 20,000 strong Brandenburg army marched out again from the Margraviate of Brandenburg heading for Strasbourg. Elector Frederick William and Electoral Prince Charles Emil of Brandenburg accompanied this army. John George II of Anhalt-Dessau was appointed Statthalter ("Governor") of Brandenburg.

Through bribes and by promising subsidies France now succeeded in persuading its traditional allies, Sweden, which had only escaped losing all of Pomerania with France's intervention in the Treaty of Oliva in 1660, to enter the war against Brandenburg. The decisive factor was the concern of the Swedish royal court that a French defeat would result in the political isolation of Sweden. The goal of Sweden's entry into the war was to occupy the undefended state of Brandenburg in order to force Brandenburg-Prussia to withdraw its troops from war zones in the Upper Rhine and the Alsace.

Preparations for war Chronology: 1674 25 December – Invasion of the Uckermark by Sweden 1675 from 4 February – Occupation of the Neumark and Hither Pomerania; followed by establishment of winter quarters Early May – Start of the Swedish spring campaign 15 May – 21 June – Battle of Löcknitz, breakthrough the Rhine line; occupation of all Havelland 6 June – Decampment of the Brandenburg Army from Franconia 21 June – Brandenburg Army reaches Magdeburg 22 June – Swedish advance party reaches Havelberg; the main body remains in Brandenburg (Havel) 25 June Brandenburg ambush at Rathenow 26 June – First Battle of Fehrbellin 27 June – Battle of Nauen 28 June – Battle of Fehrbellin The Swedes then began to assemble an invasion force in Swedish Pomerania. From September more and more reports of these troops movements were received in Berlin. In particular, the Governor of Brandenburg notified his Elector in early September of a conversation with the Swedish envoy, Wangelin, in which he had announced that about 20,000 Swedish troops would be available in Pomerania before the end of the month.Michael Rohrschneider: Johann Georg II. von Anhalt-Dessau (1627–1693). Eine politische Biographie, p. 233 The news of an impending attack by the Swedish army grew stronger when, in the second half of October, the arrival in Wolgast of the Swedish commander-in-chief, Carl Gustav Wrangel, was reported.

John George II of Anhalt-Dessau, clearly troubled by news of the troop build-up, asked Field Marshal Carl Gustav Wrangel several times in late October, through Brandenburg colonel, Mikrander for the reasons for these troop movements. Wrangel, however, failed to answer and refused another attempt at dialogue by the Prince of AnhaltSamuel Buchholz:Versuch einer Geschichte der Churmark Brandenburg, Vierter Teil: neue Geschichte, p. 92 In mid-November the governor, John George II, had received assurance of an impending Swedish invasion, but in Berlin the exact causes and motives for such imminent aggression remained unclear.Michael Rohrschneider: Johann Georg II. von Anhalt-Dessau (1627–1693). Eine politische Biographie, p. 238

In spite of the disturbing news coming from Berlin, Frederick William himself did not believe that there was an imminent Swedish invasion of the Margraviate of Brandenburg. He expressed this in a letter to the Governor of Brandenburg on 31 October 1674, which stated: "I consider the Swedes better than that and do not think they will do such a dastardly thing."

The strength of the assembled Swedish invasion army in Swedish Pomerania before they entered the Uckermark at the end of December 1674 was, according to the contemporary sources in the Theatrum Europaeum as follows: Infantry: eleven regiments with a total of 7,620 men.Anonym: Theatrum Europaeum, Vol. 11, p. 566 Cavalry: eight regiments, totalling 6,080 men. Artillery: 15 cannon of various calibres.

The forces available on 23 August 1674 to defend the Margraviate of Brandenburg, following the departure of its main army for Alsace, were pitiful. The Elector had few soldiers, and they were mainly old or disabled. The few combat-capable units at his disposal were stationed in fortresses as garrison troops. The overall strength of the garrison troops that the Governor had at his disposal at the end of August 1674 was only around 3,000 men.Curt Jany: Geschichte der Preußischen Armee. Vom 15. Jahrhundert–1914. Vol. 1: Von den Anfängen bis 1740. 2., expanded edn.: Geschichte der Preußischen Armee. Vom 15. Jahrhundert–1914. Vol. 1: Von den Anfängen bis 1740. 2., expanded edn., p. 230 In the capital city, Berlin, there were at the time only 500 older soldiers, left behind due to their limited fighting ability, and 300 new recruits.Michael Rohrschneider: Johann Georg II. von Anhalt-Dessau (1627–1693). Eine politische Biographie, p. 234 The recruitment of fresh troops had therefore to be enforced immediately. In addition, the Elector ordered the Governor to issue a general call up to the rural population and the towns and cities, in order to compensate for the lack of trained soldiers. The so-called Landvolkaufgebot ("people's call up") went back to medieval legal standards in the state of Brandenburg, by which farmers and citizens could be used in case of need for local defence. But only after protracted negotiations between the Imperial Estates, towns and cities on the one hand and the privy councillors and the Governor on the other hand did the state succeed at the end of December 1674 in enforcing the call up. Most of this edict was applied in the residenz towns of Cölln, Berlin and Friedrichswerder (8 companies of 1,300 men).Curt Jany: Geschichte der Preußischen Armee. Vom 15. Jahrhundert–1914. Vol. 1: Von den Anfängen bis 1740. 2nd revised edition, p. 236 It was also successfully employed in the Altmark to mobilize farmers and heathland rangers (mounted forestry personnel familiar with the terrain) and for defence. The governor received more reinforcements at the end of January 1675 through the dispatch of troops from the Westphalian provinces.

Invasion

Occupation of the Margraviate (25 December 1674 – April 1675)

On 15/25 December 1674 Swedish troops marched through Pasewalk and invaded the Uckermark without a formal declaration of war. In fact, according to a message from the Swedish field marshal, Carl Gustav Wrangel, to the Brandenburg envoy, Dubislav von Hagen, on 20/30 December 1674, the Swedish Army would leave the Mark of Brandenburg as soon as Brandenburg ended its state of war with France. A complete break of relations between Sweden and Brandenburg was not intended however.Michael Rohrschneider: Johann Georg II. von Anhalt-Dessau (1627–1693). Eine politische Biographie, p. 239

Figures relating the initial strength of this army, almost half of which was to consist of Germans by spring, vary in the sources between 13,000 and 13,700 men and 15 guns.

To support Field Marshal Carl Gustav Wrangel, who was over 60 years old, often bedridden and suffering from gout, field marshals Simon Grundel-Helmfelt and Otto Wilhelm von Königsmarck were appointed alongside him. However, this unclear assignment prevented, inter alia, clear orders being issued, so that directions for the movement of the army were only put into effect very slowly.Friedrich Ferdinand Carlson, Geschichte Schwedens – bis zum Reichstage 1680. p. 603

The entry of Sweden into the war attracted the general attention of European powers. The military glory of the Thirty Years' War had made the military power of Sweden seem overpowering in the eyes of her contemporaries. German mercenaries willingly offered their services to the Swedes. Some German states (Bavaria, the Electorate of Saxony, Hanover, and the Bishopric of Münster) agreed to join the Swedish–French alliance.Friedrich Ferdinand Carlson, Geschichte Schwedens – bis zum Reichstage 1680. p. 602

The Swedish Army established its headquarters at Prenzlau. It was joined there another department, established in Swedish Bremen-Verden, under General Dalwig.

At the same time, after the defeat of imperial Brandenburg in the Battle of Turckheim against the French on 26 December 1674, Brandenburg's main army marched to its winter quarters in and around Schweinfurt, reaching the area on 31 January 1675.Friedrich Förster, Friedrich Wilhelm, der grosse Kurfürst, und seine Zeit, p. 127 Because of wintry weather and the losses he had suffered, the Elector decided that he would not deploy his main army immediately on a new campaign in the Uckermark.Friedrich Förster, Friedrich Wilhelm, der grosse Kurfürst, und seine Zeit, p. 131 In addition, a sudden withdrawal from the western theatre of war would have alarmed Brandenburg-Prussia's allies – thus achieving the ultimate goal of the Swedish invasion, i.e. to force Brandenburg to withdraw from the war with France.