Battle of Tampere
1918 CE.
Shown on the map at 61.500°, 23.750°.
The Battle of Tampere was a 1918 Finnish Civil War battle, fought in Tampere, Finland from 15 March to 6 April between the Whites and the Reds. It is the most famous and deadly of all the Finnish Civil War battles. Its bloody aftermath saw the Whites execute hundreds of captured Reds with another 11,000 prisoners sent to the Kalevankangas camp.
Text from the Wikipedia article Battle of Tampere, licensed CC BY-SA 4.0.