It’s safe to say that the Finnish were brilliant and unconventional when it came to war tactics, and they proved that during Winter War. They had this Motti tactic to immobilize and destroy Soviets army columns by blocking the road with a bundle of logs. There was also this one bizarre time when they annihilated an entire Soviet battalion who stopped their attack to eat Finnish sausage stew they found while overrunning their mess tents. The tactics continued during the Continuation War. In this particular instance, they utilized a folk song called Säkkijärven polka to stop the Soviet mines from detonating.
When the Winter War between the Soviet Union and Finland ended in 1940, they signed the Moscow Peace Treaty, and a ceasefire immediately followed. However, the peace did not last long. The hostilities resumed just 15 months after the Winter War ended when Finland decided to ally with the Nazis to invade. They wanted to regain the territories they lost in the Winter War. This second conflict was called Continuation War.
The Finns succeeded in taking back the city of Vyborg from the USSR, driving Red Army units into a retreat. Of course, the Soviets wouldn’t just back down without a fight, so they rigged the city with mines and explosives while retreating. There were so many of these mines that many Finnish soldiers died from their explosions, and civilians were not allowed to return to their homes even after the city was reclaimed.
What confused the Finns was that the mines kept detonating, even when no one was setting them off. The initial theory was that these mines were set on timers, it was not until August 1941, when they discovered 1300 pounds of explosives along with its triggering device. They found out that these mines were not rigged with timers but triggered through radio signals.