Editing Axel Oxenstierna (section)

===1630–1636: Oxenstierna in the Thirty Years' War===
When Sweden entered the [[Thirty Years' War]] in the summer of 1630, tolls from Oxenstierna-controlled Prussia, as well as food supplies acquired by Oxenstierna, were pivotal assets.<ref name="Nordisk Familjebok - Axel Gustafsson Oxenstierna" /> He had also obtained credits from foreign businessmen, ensuring large sums of money making it possible to hire mercenary soldiers to the army used in Germany.<ref name="Trettioåriga kriget"/>

After the [[Battle of Breitenfeld (1631)|Battle of Breitenfeld]] on 7 September 1631, Oxenstierna received a summons to assist the king with his counsels and co-operation in Germany. During the king's absence in [[Franconia]] and [[Bavaria]] in 1632 he held the appointment of ''legatus'' in the [[Rhineland]], with plenipotentiary authority over all the German generals and princes in the Swedish service. Although he never fought a battle, he frustrated all the efforts of the Spanish troops by using strategically successful regulations.{{Clarify|date=August 2018}} He managed to conduct large reinforcements to King Gustavus through the heart of Germany in the summer of 1632.<ref name="Encyclopædia Britannica"/>

In the [[Battle of Lützen (1632)]], on 6 November 1632, Gustavus Adolphus died.<ref name="Trettioåriga kriget - Gustavus death">{{cite book|last=Ericson Wolke|first=Lars|author2=Larsson, Villstrand|title=Trettioåriga kriget|year=2006|editor=Historiska Media|pages=125|publisher=Historiska media |isbn=91-85377-37-6|language=sv}}</ref> This meant that Oxenstierna became supreme commander of the Swedish troops in Germany, although he let his subordinate generals be responsible for the military operations on a lower level. He moved his headquarters to [[Mainz]], which in practice became the new Swedish capital.<ref name="Trettioåriga kriget"/> Oxenstierna was now absolute ruler of the significant area that the Swedish army had conquered in Germany. He was offered the position as prince-elector of Mainz, but, after serious considerations, the offer was turned down.<ref name="Nordisk Familjebok - Axel Gustafsson Oxenstierna" />

When King Gustavus died in November 1632, his only legitimate and surviving child, [[Christina of Sweden|Christina]], was almost six years old. Until her declaration of majority at 18, a [[Privy Council of Sweden|regency council]] ruled Sweden. This council was headed by Lord High Chancellor Oxenstierna, who wrote [[Instrument of Government (1634)]], a new constitution. During the years after the king's death, it became apparent that differences of opinion existed within the council. Some of Oxenstierna's colleagues recommended that Sweden should seek peace and withdraw from the war in Germany, not least after the defeat at [[Battle of Nördlingen (1634)|Nördlingen]] in 1634. However, Oxenstierna's opinion, that Sweden should remain in the war to ensure compensation for the sacrifices made, prevailed.<ref name="Trettioåriga kriget"/> The, for the Swedish side, disastrous outcome at Nördlingen brought him, for an instant, to the verge of ruin and compelled him for the first time so far to depart from his policy of independence as to solicit direct assistance from France. But, well aware that [[Cardinal Richelieu|Richelieu]] needed the Swedish armies as much as he himself needed money, he refused at the Conference of Compiègne in 1635 to bind his hands in the future for the sake of some slight present relief. In 1636, nevertheless, he concluded a fresh subsidy-treaty with France at [[Wismar]].<ref name="Encyclopædia Britannica"/> Swedish troops remained in Germany all the way until 1648 and the Thirty Years' War's end.<ref name="Trettioåriga kriget - End of War">{{cite book|last=Ericson Wolke|first=Lars|author2=Larsson, Villstrand|title=Trettioåriga kriget|year=2006|editor=Historiska Media|pages=180|publisher=Historiska media |isbn=91-85377-37-6|language=sv}}</ref> Oxenstierna, however, left Germany and returned to Stockholm in 1636, after ten years duty as premier Swedish representative in Prussia and Germany.<ref name="Trettioåriga kriget"/>