"Fria Kriget" (lit. "The Free War") is a form of guerrilla warfare typically associated with the Swedish Armed Forces during the Cold War but is still present in modern Swedish military doctrine as a standing order. The free war is designed for the sub-company level (platoons, squads).
The free war has it's origins in World War 2. While Sweden was not directly involved in combat during the war, the small, unaligned nation was heavily militarized. In the closing years of the war, the perceived Soviet threat to the nations in the Baltic Sea region became increasingly real. The tendency of the Soviets to occupy liberated territories worried the Swedish government and consequentially, Sweden adjusted its military doctrine and organization to face a potential Soviet invasion.
The free war was based on the Finnish defence tactics during the Winter War but with significant modifications. The first official mention of the free war comes in the publication "Anvisningar för fria kriget" (lit. "Guidelines for the free war") from 1944.
The primary difference between free war and other forms of guerrilla warfare is that the free war is to be conducted by regularly trained and (initially) well-equipped military units, as opposed to paramilitary or resistance organizations.
During late WW2 and going into the Cold War era, the Swedish Armed Forces decentralized it's organization and supplies heavily with the intent of making it near impossible for an enemy (the Soviets) to stop the national military mobilization. One measure taken in this decentralization effort was to establish so called "mobiliseringsförråd" (lit. "mobilization storage") in rural locations. These mobilization storages were often so secret that approaching them in military vehicles was strictly prohibited so as not to uncover their location. The mobilization storages contained a wide variety of items, ranging from eye-patches and bandages to weapon systems and even vehicles.
On a side-note, we can quickly cover mission command (auftragstaktik, mission-type tactics) which permeates through the entire Swedish Armed Forces since the before the 1950's. Mission command is an approach to leadership that builds on mutual trust between commanders and their subordinates where the commander issues an order on what to achieve and it is up to the subordinate commander to figure out how to achieve that objective.
On another side-note, we can talk about the road bases that Sweden established throughout the country during the cold war. Road bases are essentially regular, straight roads that have been widened and/or had the treelines on either side of the road pushed back to allow aircraft to land. In connection to these road bases would be resupply facilities and in certain cases even command & control centers.
The free war is predominantly conducted by small-scale raids and ambushes on rear-echelon and support troops (command posts, artillery, logistics, etc) with the intent being to force the opponent to allocate more resources to rear-echelon security, thus reducing the amount of units at the main confrontation line.
While the free war emphasizes that the units involved in the conduct of it are meant to disturb and harass the enemy force, the ultimate goal should be to rejoin their unit to either (1) be reintegrated into their operations, or (2) coordinate a continued free war.
Under no circumstances should a unit conducting the free war abandon international laws of conflict.
In Swedish doctrine, rear-echelon areas are also where jägarförband (rangers) conduct battle, though their presence in these areas are intentional and planned, whereas the free war is a final resort for unintentionally being cut-off from friendly forces.
In conducting the free war, the unit should utilize societal resources, taking into account the livelihood of the civilian populace. It is also encouraged for the unit to capture and make use of enemy resources.
It is a well-known standing order within the Swedish Armed Forces that "any information that resistance is to cease, is false". The Swedish Armed Forces also has a standing order with regard to free war; "all units cut-off from higher levels of command shall disrupt his operations."
The free war is designed to deter a foreign power from invading Sweden by forcing the opponent to allocate resources from other areas to deal with resistance from Swedish military units, regardless of territorial victories. It is a unique form of warfare that is rarely discussed due to it's exotic nature.
Handbok Markstrid - Pluton (2016)
Handbok Markstrid - Grupp (2016)