Hans Dietrich von Seeckt was one of two admirals placed in command of Iserlohn Fortress, some time after the Fourth Battle of Tiamat, along with Thomas von Stockhausen, replacing the former commander, admiral Gregor von Muckenberger. Stockhausen commanded Iserlohn Fortress, while Seeckt was in command of Iserlohn's garrisoned fleet.
When the Rosen Ritter siezed control of Iserlohn's command center in the Fifth Battle of Tiamat, Seeckt acted against the advice of his subordinate, Paul von Oberstein, and decided to wait and see what would happen, giving Yang Wenli time to completely pacify the imperial forces within Iserlohn. With control of the Fortress, Yang Wenli sent out the 13th Fleet from Iserlohn, successfully baiting Seeckt. Seeckt advanced his fleet toward the FPA's 13th fleet, and into the range of Iserlohn's main cannon, the mighty Thor Hammer.
Yang Wenli destroyed more than 1000 Imperial warships with the first shot, and advised Seeckt to either surrender or withdraw from battle. Seeckt refused to do either, and informed Yang Wenli of his intent to fight to the death, even if the battle was hopeless--his personal code of honor demanded as such.