The conflict known as the Battle of Mandalore took place in 4 ABY amidst the Nagai incursion.
The defense of the planet was spearheaded by Fenn Shysa; however, his troops were unable to hold off the Nagai. Shysa, accompanied by his comrades, such as the half-Corellian Bey, fell back to the Alliance of Free Planets installation situated on Endor. There, after proving themselves capable pilots for the Alliance, they managed to get some retribution in the Second Battle of Endor.