The Deputy Führer possessed the ability to give out decorations, such as the Iron Cross, to Ekosians performing various acts on behalf of the "fatherland".
In theory, the person holding this position was subordinate to the Führer and was supposed to carry out his orders. This thinking, however, was not borne out in reality. Melakon drugged Gill to the point of psychosis and controlled the Ekosian government himself. The people at large were not aware of this and assumed that he was acting on behalf of Gill. He was eventually killed by the ZeonIsak, after finally killing Gill. (TOS: "Patterns of Force")
In the original Nazi Germany, this position was held by Rudolf Hess from 1933 until 1941, when it was abolished.