This stone was erected in memory of the Swedish king Gustavus Adolphus (Gustav II Adolf, 1594–1632) in Peenemünde on the Pomeranian island of Usedom in 1930, 300 years after his landing there at the head of an army of 13,000 men on 6 July 1630. Sweden had by that date already declared its entry into the Thirty Years' War. Gustavus Adolphus' intervention in the war in Germany suddenly made a victory of the Catholic, imperial, Habsburg side far less likely. Sweden secured a hegemonic position in northern Europe up until the early 18th century and in doing so helped preserve German Protestantism.
Memorial stone to Gustavus Adolphus (erected 1930), colour photograph, 2013, photographer: Chron-Paul; source: Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Peenem%C3%BCnde-Gustav-A-090903-023.jpg, Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) https://creativecommons.org/licenses/by-sa/3.0/deed.en.