The Huns are minions of Shan Yu in the movie Mulan. They traveled with him through the great wall. The five main Huns start by barginmg through the Great Wall and try to kill a guard but are unsuccessful. Shan Yu spares the guard's life only because so he inform the emporer. The Huns capture two Imperial Scouts. Shan yu leaves one of them live so he can tell his own emperor to send his strongest armies. The massive Hun army (includes the main ones) burning down villages.
They almost made it through the mountain pass until Mulan caused an avalanche destroying most of the army except for Shan Yu and the few who survived after Mushu fired a cannon accidentally causing Li Shang's position to given away to the Huns. The five surviving Hun henchmen hide inside a fake paper dragon during the celebration the "defeat" of the Huns. When Hayabusa, Shan-Yu's falcon retrieve Shan Yu's sword, the Huns burst out of the dragon s and kidnap the emperor. Shan Yu surprises the emperor by hanging upside down and saying "Boo". Shan Yu orders the Huns to guard the door. However Shang's three main soldiers trick the Huns by dressing as Calcubine girls. Then they attack the Huns. some of them have time to attack back but are defeated unconscious by Mulans and soldiers. Its unknown what happened to the survivors after Shan Yu's death.
It is possible that the surviving Huns did survive sense they were just seen being knocked out. It is possible they fled and went into hiding. This is unknown since they did not appear in the sequel of Mulan.