 In 1848, Jachmann received his first command, the corvette ; through the 1850s and early 1860s, he held several other commands, including the frigates —aboard which he took part in the Eulenburg expedition to East Asia—and .During the Second Schleswig War in 1864, he commanded Prussian naval forces in the Baltic from "Arcona", and led a small squadron at the Battle of Jasmund on 17 March.Though defeated in that battle, he was promoted to "Konteradmiral" (rear admiral) for his aggressive handling of the Prussian fleet.