Kammala wannan jumla: A farkon yakin Schleswig na biyu a 1864, yawancin jiragen ruwa na Prussian sun kasance a cikin Baltic Sea. Yarima Adalbert shi ne babban kwamandan sojan ruwa, kuma Jachmann, a matsayin babban kyaftin din, ya zama kwamandan rundunar, tare da "Arcona" a matsayin babban jirginsa. Mafi yawan manyan jiragen ruwa na Danish sun kewaye manyan tashar jiragen ruwa na Prussia, suna kama jiragen ruwa na Jachmann - "Arcona" da "Swinemünde". Ranar 17 ga watan Maris, Jachmann ya ɗauki jirgi biyu da jirgin ruwa mai dauke da makamai don kalubalanci sojojin Denmark. A cikin abin da ya biyo
Yaƙin Jasmund daga tsibirin Rügen, rundunar Jachmann ta ci nasara da rundunar sojojin Denmark mafi karfi kuma aka tilasta masa komawa baya. Wannan shi ne kawai babban yakin da aka yi a cikin Baltic a lokacin yakin. Duk da haka, an nada shi "Konteradmiral" (Rear Admiral) saboda mummunan aikinsa na rundunar jiragen ruwa a Jasmund. Zuwan wani jirgin ruwa na jirgin ruwa na Danish ya hana duk wani hare-haren da ake yi a kan jiragen ruwa na Danish, kamar yadda bindigogi na gargajiya da ke dauke da makamai na Jachmann ba su da amfani a kan jirgin ruwa.