After the Treaty of Coruscant, Balmorra was granted to the Sith Empire. Due to this, all Republic forces still on the planet from the Great Galactic War were supposed to leave the planet, but some managed to stay behind. These soldiers banded together with Balmorran citizens to form the Balmorran Resistance movement, whose main goal was to end the Empire's occupation of Balmorra.
The Resistance would carry out guerilla warfare against the Imperial occupation. Not just soldiers were carrying out these tactics, but regular citizens as well. This made it more difficult for the Empire to discover who was a part of the Resistance, because it could have been anyone. Thousands of these members would also use dangerous and hidden locations that the Empire would never suspect, to meet and train, making detection even harder.
Not all of the Balmorran people agreed with the Resistance, and felt they were abandoned by the Republic and should accept the Empire and its governor, Darth Lachris. Those that were a part of the Resistance, however, would have done anything to remove it from the planet, even die.