In January 1631, Swedish forces garrisoned in the Pomeranian bridgehead proceeded southwards, and sacked the Pomeranian towns of Gartz (Oder) and Greifenhagen (now Gryfino) near Pomerania's border with Brandenburg.[3] Further southward advances along the Oder into the territory of George William, Elector of Brandenburg followed, and on 23 January 1631, Sweden allied with France in the Treaty of Bärwalde, concluded in Brandenburgian Bärwalde (now Mieszkowice).[3]
Siege and storm of Frankfurt
The Swedish forces, commanded by Gustavus Adolphus,[4] were supported by Scottish auxiliaries commanded by John Hepburn and Robert Monro.[5] They laid siege on the town for two days, and stormed it on the second day.[4] The assault was successful and resulted in the sack of the town.[4][5] The success was in part due to internal quarrels in the defending force—mercenaries who had not been paid refused to fight without receiving their pay first.[4] The defenders were "slaughtered [...] where they stood" and suffered 3,000 deaths, compared to 800 casualties on the Swedish side.[8] Many deaths occurred when the town was looted.[5]
Aftermath
Scottish major general in Swedish service John Leslie was appointed governor of the town and gave orders to have its defenses strengthened and the thousands of bodies buried.[5] The latter task was achieved by digging mass graves for over a hundred bodies each; after six days, all dead had been buried.[8] John Leslie was soon succeeded as Frankfurt's governor by another Scot, James MacDougal, who was in turn succeeded by a third Scot, Alexander Leslie.[5]
The battle is mentioned as happening on Palm Sunday 1631 in contemporary sources.[1] This was on 13 April for congregations using the Gregorian calendar (most Catholic nations) and 3 April for those still using the Julian calendar.[2] Krause & Balz (1993) give 15 April.[3]
Brzezinski, Richard; Turner, Graham (2001). Lützen 1632: climax of the thirty years war. Volume 68 of Osprey campaign series. Osprey Publishing. ISBN1-85532-552-7.