The Soviet army was poorly prepared for winter warfare, particularly in forests, and relied on vulnerable motorized vehicles. These vehicles were kept running continuously so their fuel would not freeze, which led to increased breakdowns and aggravated fuel shortages.
One of the most remarkable losses in military history is the so-called “Raatteentie Incident,” during the month-long Battle of Suomussalmi. The Soviet 44th Infantry Division (c. 25,000 troops) was almost completely destroyed after marching on a forest road straight into an ambush of the Finnish “Kontula detachment” (a unit of 300 men).
This small unit blocked the advance of the Soviet Division, while Finnish colonel Hjalmar Siilasvuo and his 9th Division (c. 6,000 troops) cut off the Soviet retreat route, divided the enemy force into smaller units and then destroyed it in detail. The Soviet casualties amounted to up to 23,000 men, while the Finnish lost around 800 men. In addition, the Finnish troops captured 43 tanks, 71 field and anti-aircraft cannons, 29 anti-tank cannons, AFVs, tractors, 260 trucks, 1,170 horses, infantry weapons, ammunition, medical and communication material.
From British Movietone News 4th January 1940: