The "forest brethen" were a scarcely known anti-imperialist guerrilla movement against the Soviet yoke in the middle of Europe. A notable historian testifies the origins and development of the guerrilla movement:
A striking feature of the postwar Stalinist era in Estonia was the protracted existence of an anti-Soviet guerrilla movement. This phenomenon began to emerge with the rapid Nazi retreat, which stranded thousands of Estonian soldiers who had been drafted into the German army in Estonia. Although some of these men still managed to leave Estonia, many disappeared into the woods and became "forest brethen" (METSAVENNAD, the popular Estonian term for the guerrillas).* Their numbers were supplemented in the fall of 1944 by other German army veterans and members of Home Guard seeking to avoid the arrest by Soviet security forces. The Soviet authorities carried out two mobilizations in the fall of 1944 and spring of 1945, and this action prompted still others to join the guerrillas or go underground. In addition, those seeking revenge against the Soviet regime for the mass deportations associated with collectivization in March 1949 formed a final source of replenishment for the guerrillas.**
Documentation on the guerrilla movement remains sparse, but reports by eyewitnesses permit an overall assessment. The organization of the forest brethen varied, ranging from relatively large military units to individuals operating alone. Arms and ammunition abandoned by the retreating Germans outfitted the Estonian guerrillas in the early postwar years, and subsequent Soviet military supplies became available as the spoils of battle. Food and other basic necessities, along with strategic information, came from the surrounding local population. Regionally, the guerrillas were strongest in Virumaa, Pa"rnu and V6rumaa, among the most swampy and thickly wooded areas of Estonia.
The size of guerrilla forces is difficult to determine, but one estimate suggests that there were about 5,000 forest brethen in 1944-46 with 80 percent located in the three above-mentioned districts. In some localities in the early postwar years the guerrillas had effective military control. The high point of guerrilla strength probably came in 1946-1948, when they were capable of fighting substantial military engagements with Soviet forces. Gradually, however, casualties and psychological attrition thinned their ranks. By the early 1950s, despite new blood as a result of the collectivization drive, guerrilla strength had begun to ebb. A post-Stalin amnesty, carried out as promised in 1955, virtually ended the movement.***
The goals of forest brethen must be seen in the context of an expected postwar restoration of Estonian independence through the good offices of the Western Allies. Thus, although the guerrillas realized that they had no hope of bringing down the Soviet regime, they intended to hold out until international pressure (or perhaps a new war) forced the Soviets to withdraw from Estonia. In addition to guarding themselves, the guerrillas sought to protect the local population from acts of violence. By the time of mass collectivization in 1949, the dream of restored independence had vanished, and the major guerrilla motivation became revenge against the Soviet regime. For those slated for deportation, joining the forest brethen was the only other choice.
Source: Toivo U. Raun: Estonia and the Estonians. Hoover Institution, Stanford University. Studies of Nationalities in the USSR Series. Hoover Press, Stanford, California 1987 (pp. 174-175) (In Finnish: Viron historia, Otava 1989 (s. 217-218). Read and consult the book - the best survey of the whole Estonian history!
* Soviet publications invariably refer to the pro-independence guerrillas as "bandits".
** Purre: "Teine punane okupatsioon" (Second red occupation - TH): 1944-1950, pp. 22-24, 31-32; Olaf Tammark: "Mehed kogunevad metsadesse" (Men gather in the woods - TH), in EESTI SAATUSAASTAD 2: 81.
*** Eerik Heine: "Metsavennad" (Forest brethen - TH), in EESTI SAATUSAASTAD 2: 66-75; Purre, pp. 32-33, 35-36, 38-39; Meinhard Leetmaa: S6jas ja igestatud Eestis (In the war and in Estonia under the yoke -TH), Stockholm, Va"lis-Eesti & EMP, 1979, pp. 231-233; Tammark, p. 77.
**** Leetmaa, pp. 230-231; Purre, 38-39; Rein Taagepera: "Soviet Documentation on the Estonian Pro-independence Guerrilla Movement", 1945-1952", Journal of Baltic Studies 10 (1979): 101-2, 105.