The 'Battle of Kollaa' was fought between Soviet and Finnish forces in the Ladoga Karelia region to the north of Lake Ladoga within the context of the Soviet-Finnish winter war known to the Finns as the 'Talvisota' (7 December 1939/13 March 1940).

Despite having far fewer men than were deployed by the Soviets, Eversti Einar Vihma’s (from 18 December Eversti Per Ekholm’s) Finnish 12^th Divisioona checked the Soviet forces as the latter were prepared to operate only along roads. There were only a few roads in the Kollaa area, and all of these were held by Finnish troops, making it impossible for the Soviet forces to proceed, especially as they lacked the skis necessary for cross-country movement.

Some 47 miles (76 km) long, the Kollaa river emerges from the Kollasjärvi lake and flows to the Tulemajärvi lake, and is generally considered to have been one of the most difficult locations to defend during the 'Talvisota'. The Soviets are estimated to have fired nearly 40,000 artillery rounds at the Finns' defence line per day whereas, in contrast, the Finnish artillery could fire a maximum of 1,000 rounds per day.

The 'Battle of Kollaa' continued until the end of the 'Talvisota' as the 12^th Divisioona halted Komdiv Ivan N. Khabarov’s (from 13 December General Polkovnik Grigori M. Shtern’s) Soviet 8^th Army, and most particularly Kombrig Mikhail S. Evstigneyev’s 56^th Division, in an attritional battle which cost each side heavy casualties. The Soviet forces managed to penetrate the Finnish defence line in Kollaa several times, pushing the Finns out of their positions, but the Finns then restored the integrity of their defence line through systematic counterattacks. On 12 March, near the end of the war, the Soviets managed to establish a breakthrough area between 545 and 1,635 yards (500 and 1500 m) deep in the Finnish defence line, almost triggering a Finnish collapse as Hägglund considered the abandonment of the main defence line along the Kollaa river. However, as the news from the sector was that the situation was 'not yet that alarming', he in fact ordered a counterattack to retake the defence line on the following day. These orders were rescinded as news of the newly-signed peace treaty reached the front, and the men were instead ordered to hold their current positions until the end of hostilities.

It is worthy of note that the legendary Finnish sniper Simo Häyhä served on the Kollaa front. He is credited with 200 confirmed 'kills' according to Finnish military records, but the true number remains contested and is believed to have been considerably more than the official figure.