 Later that year, Jachmann accompanied Roon aboard "Loreley" for a survey of the Jade Bay, where the naval base at Wilhelmshaven was planned.Jachmann remained in his post in the Baltic Sea during the Austro-Prussian War, commanding the main squadron of frigates and corvettes.Before the outset of hostilities, he sent the gunboat to Elbe to block the movement of an Austrian brigade that was garrisoned in Holstein.