Struma operation
1916 CE.
Shown on the map at 40.786°, 23.849°.
The Struma operation was the occupation of a part of northeastern mainland Greece by the Bulgarian army during the First World War between 17–23 August 1916. It was named after the Struma (Strymonas) river.
Text from the Wikipedia article Struma operation, licensed CC BY-SA 4.0.