Swedish intervention in the Winter War

The Swedish Intervention in the Winter War was a short-lived but successful attempt by the Swedish Volunteer Corps, along with other Nordic volunteers, to prevent a Soviet invasion of Finland during the Winter War. The volunteers only engaged in a few skirmishes on ground and in the air, the only major battles they participated in being the battles of Salla and Honkaniemi.

Source: Wikipedia — Swedish intervention in the Winter War (CC BY-SA 4.0)