- Main article: Hundred Days War
Within a month after the outbreak of the Hundred Days War, the Imperial Army of Erebonia had occupied nearly all of the Liberl territory except for Leiston Fortress and the Grancel region, which remained in remained in opposition.
Unbeknownst to the Imperial army, three patrol ships were quietly being developed behind the walls of Leiston Fortress. Upon completion, they were put under the direction of veteran commander General Morgan. A large scale counterattack was launched and the outcome of the war was tipped in Liberl's favour.
Thanks to Leiston's opposition during the war, it is now considered as an impregnable fortress.