Dxun
Despite being temperate and habitable, the jungles of Dxun posed major challenges for everyone struggling to survive there. Due to its constant rains and wet climate, mechanical devices did not last long and required continuous maintenance. Moreover, the jungles were inhabited by many dangerous predators, such as cannoks, bomas, maalraas, and zakkegs, forcing the moon's inhabitants to be armed at all times.
Though considered a moon of Onderon, Dxun and Onderon were almost sister planets. They were so close to one another that it was only a short shuttle ride between them, and they even shared a bit of the same atmosphere. Every year, during Dxun's summer season, the atmospheres of Onderon and Dxun would connect, allowing the vicious Dxun beasts to set foot on Onderon and settle there, thus laying the foundations for the Beast Wars.
Mandalorian Wars
After assuming the leadership of the Mandalorians, Mandalore the Ultimate made Dxun his stronghold, from which he planned his attack on the Galactic Republic.
In 3,963 BBY, the Mandalorian Wars expanded into a galaxy-wide conflict when the Mandalorian Neo-Crusaders began their invasion of the Republic. From their headquarters on Dxun, Mandalore's forces attacked and took nearby Onderon in mere hours. A battle with the Republic forces took place on the moon, but it was little more that a rear-guard holding action by the Republic.
Years later, after the Jedi Revan and Malak had entered the war and pushed the Mandalorian forces back to their original Dxun staging-grounds, a far more bloody battle was fought. The Republic attempted to capture the Mandalorian headquarters on Dxun. Republic forces managed to defeat the Mandalorians, but the victory came at a heavy cost. The Mandalorian outposts were entrenched and well defended by hidden mines, traps, anti-air turrets, and the ferocious inhabitants of the jungle itself. During the bloody battle, the Republic lost ten soldiers for every Mandalorian killed. The Jedi Exile who was in command of the battle, was forced to sacrifice dozens of her soldiers, sending them on a suicidal charge to disable the minefield that was the last obstacle keeping them away from the Mandalorian fortress.
After the battle, the Republic military did not bother to demolish many structures that the Mandalorians had built, neither did they uncover the many, hidden weapons caches providently left in case the Mandalorians were someday to return.