On December 30, 1919, in view of the growing Bolshevik threat, the Latvian government signed an agreement with the Polish authorities about the military cooperation against the common enemy. The sides agreed on conducting military action in the territory of Latgale (southern Latvia). 40000 soldiers under the command of General Edward Rydz-Śmigły had to attack the Kawasławaka-Wyszki-Dubna line on January 3, 1920 and to secure the contact between Latvian and Polish troops. The action had a cryptonym “Winter” and all preparations to it were held in secret. The established alliance became the basis for good Polish-Latvian relations up until the falling of the Second Republic of Poland.
Figure: Graves of Poles who died in battles in the south of Latvia, from the collection of the National Digital Archive