Partisans
Partisans are members of an irregular military force, formed to oppose control of an area by a foreign power or an army of occupation, by some kind of insurgent activity.
Definition
Partisans may be unlawful combatants, if they engage in armed conflict in violation of the internationally agreed on laws of war, which means that they are not protected by such laws and rights. The occupier may consider partisans to be "terrorists", the partisans may consider themselves to be "freedom fighters", sometimes they are, like the German Freikorps soldiers during the Napoleonic Wars.
WWII
The term has in particular been applied to insurgents during WWII, German counter-warfare was termed anti-gang combat (Bandenbekämpfung).
Hague Convention of 1907
The Hague Land War Code of 1907 sought a compromise based on the franc-tireurs (French and Belgian snipers of the Franco-German War of 1870/71 who acted insidiously): as a condition for the improvised warrior with an improvised uniform to be recognized as a combatant in the sense of international law , the final act of the Second Conference demands: responsible superiors, widely visible badges and open carrying of weapons. If soldiers are attacked by non-combatants, they are allowed to retaliate with the weapons at their disposal, including the right to retaliate against the civilian population, as seen in World War II, e.g. against Greek partisans during Operation Merkur or against Italian partisans by Erich Priebke after the Massacre on the Via Rasella (Massaker an der Via Rasella)..