From Wikipedia:

The Weapons Cache Case was a Finnish criminal case of the mid-1940s. It concerned a secret military operation following the Continuation War, where a large number of Finnish Army weapons and equipment was hidden away around the country.

Following the Moscow Armistice, two officers in Finnish Military HQ, Colonel Valo Nihtilä and Lieutenant Colonel Usko Haahti, started planning countermeasures against a possible Soviet occupation of the country. They came up with the idea of decentralized storing of light infantry weapons, so that in case of occupation, an immediate guerrilla war could be launched.

During the demobilization, an organization responsible for hiding the equipment was created and war material was given for safekeeping. A total of 5,000–10,000 people participated in the operation. It was planned that they would hide material for 8,000 men, but the participants worked so eagerly that it is supposed they hid material for 35,000 soldiers.

The case started to unravel in the spring of 1945, when one man, who had stolen foodstuffs from the cache and sold it on the black market, for fear of reprisal from his comrades, divulged the existence of the caches to the Allied Control Commission (ACC). Initially the ACC was eager to follow the case, but after written orders from Nihtilä and Haahti surfaced, they left the investigation to Valpo, the communist-controlled state police of Finland at the time.

Valpo interrogated more than 5,000 people but failed to completely crack the case and find all the weapons. Most of the weapons were silently returned to army depots, and some were destroyed, but even today when old buildings are demolished, caches turn up every year. The investigators failed to find out how many people participated in the operation, as the participants tended to be reluctant to divulge meaningful information. In the end, 1,488 people were convicted, most of them receiving 1–4 months in prison.

Decades later, in 1980, Arvo Tuominen, a former Finnish Communist leader, claimed that the weapons cache case was the tipping point which transferred the power within the Finnish Communist movement from the revolutionary to the parliamentary wing, as the communists feared armed resistance against revolutionary takeover. However, as historian Kimmo Rentola among others has shown, Tuominen's claims are to be treated very sceptically.