Guerrilla warfare, alternatively called guerrilla tactics, is a form of combat where smaller forces engage much larger adversaries through the use of unconventional methods.
Guerrilla tactics involve smaller groups using unconventional methods against larger enemy forces. During the Clone Wars, the Republic supported and trained various militia groups, including the rebels of Onderon. During this period, Obi-Wan Kenobi agreed to assist in the training of the Onderon rebels in their struggle against Sanjay Rash, while emphasizing that he would not fight the battle for them. The Confederacy of Independent Systems also provided training to anti-Republic combatants, such as Cassian Andor's insurrectionist cell. The Onderon rebels, including Saw Gerrera, who had been trained by the Republic, would later become a problem for the Republic's successor, the Galactic Empire, as members of the Partisans. The Partisans were active at Jedha City on Jedha until its destruction by the Death Star.
In 18 BBY, the militias of Salient II employed guerrilla warfare against the Empire, an effort that ultimately failed.
Death trooper squads were also knowledgeable in guerrilla tactics, a result of their specialized training on Scarif. This expertise was demonstrated by DT-5537 during the Battle of Scarif.
The Rebel Alliance utilized guerrilla warfare to offset the numerical superiority of the Galactic Empire. Pathfinders used guerrilla combat for infiltration purposes. The Ewoks engaged in guerrilla warfare against the Empire during the Battle of Endor.
Following the Battle of Crait, the Resistance was reduced to guerrilla fighters. Despite their diminished state, they continued to oppose the First Order while striving to restore justice and the New Republic. Those who engage in guerrilla warfare are often labeled terrorists by the governments and militaries they oppose. For instance, the Separatist-backed king Sanjay Rash of Onderon declared that the Onderon Rebels, led by Lux Bonteri, Saw, and Steela Gerrera, were terrorists during the Clone Wars. Similarly, the Galactic Empire consistently regarded both the Partisans and the Rebel Alliance as terrorist organizations.