Sissi is a Finnish term for light infantry which conducts reconnaissance, sabotage and guerrilla warfare operations behind enemy lines. The word sissi, first attested in the modern meaning "patrolman, partisan, spy" in 1787, comes to Finnish from Slavic and refers either to a forest bandit or his yew bow.
The Finnish Army trained Sissi units to conduct long range reconnaissance patrols, gather intelligence from concealed observation posts, raid enemy installations (especially supply depots), conduct road side ambushes and pursue and destroy enemy special forces units. In wartime, an unspecified number of reservists were to be assigned to Sissi battalions and would deploy and operate as small groups up to company size. They were meant to either infiltrate through enemy lines to their rear, or stay behind and covertly operate against enemy forces in their area of responsibility even after regular friendly troops had been forced to retreat. Sissi battalions were part of Finnish Army "local troops", unlike the jäger and armored brigades meant for operational use.
In official Finnish military parlance, the word "sissi" has been largely phased out. For example, the Sissi company of the Lappi Border Guard of the Finnish Border Guard was renamed to "Border Jaeger Company" in 1994. The conscripts serving in the unit were concurrently renamed to Border Jaegers. Similarly, Finnish Army sissi units are now called "reconnaissance" units, and the personnel serving in them called "tiedustelija", "reconnaissance man". A notable exception are the sissiradisti or Sissi signalists.
History
Wars between Russia and Finland have a long tradition of Finnish sissi warfare. Famous sissi leaders have included Pekka Vesainen (c. 1540–1627), Tapani Löfving (1689–1777, fought during the Greater Wrath), and Olli Tiainen (1770–1833, fought during the Finnish War).
Before the hostilities of Winter War, the Finnish Borderguard formed 25 Independent Battalions (Erillinen Pataljoona) from local reservists along the border area. After the outbreak of hostilities, a further five Sissi Battalions (Sissipataljoona) were formed from "auxiliary personnel". These battalions, especially those of the latter type, were below their nominal strength in both men and weaponry. These units proved to be effective in using motti tactics in their native area with light infantry weapons and skis.
In the Continuation War the ad hoc Sissi Battalions were replaced by Independent Battalions. For example, the 4th Independent Battalion was directly under the command of Supreme Headquarters doing LRRP and raiding missions deep inside Soviet area. In the Battle of Ilomantsi, soldiers of the 4th disrupted the supply lines of the Soviet artillery, preventing effective fire support. In the Ladoga Karelia area of operations the length of the front, the absence of roads and a lack of troops prevented continuous front lines during the trench warfare period. Both armies used a chain of fortified field bases separated by the wilderness, monitoring and controlling the gaps with patrols. Both Finns and Soviets launched raids and recon patrols into enemy territory. Battles were short clashes of lightly armed infantry groups from squadron to battalion in size, with little chance of support or reinforcements.
After the Second World War, Sissi units were decommissioned and Sissi training was officially discontinued, although many units gave Sissi training for their reconnaissance units. In the beginning of the 1960s, the Paratrooper School was established at Utti, and both infantry and border guard units established Sissi training companies thereafter.
Famous sissi troops
Ilmari Honkanen, officer in 4th Independent Battalion (ErP 4). Known especially from the destruction of the Soviet military depot in Petrovski Jam. Lauri Törni a.k.a. Larry Thorne, a commander of "Detachment Törni", the reconnaissance company of the 12th Infantry Regiment during the Continuation War, had a bounty on his head by the Soviets, joined Waffen-SS in 1940 and was sent back home before the Continuation war. After the Finno-Soviet ceasefire he returned to Waffen-SS because he did not believe that Soviets would actually follow the ceasefire agreement. After the war Törni joined US Army and volunteered for the US Army Special forces. Mauno Koivisto, member of "Detachment Törni" during Continuation War, later the President of Finland. Mikko Pöllä, most decorated member of the ErP 4. Onni Määttänen. Paavo Suoranta (Peltonen). Viljo Suokas.