navigation school in Danzig and he passed his examination on 20 March 1843. He also served aboard ships on voyages to the Americas into 1844. Naval career In early 1843, as the Prussian Navy looked forward to the completion of the corvette , it began searching for cadets at the Danzig navigational school to form the ship's crew. Jachmann was one of those studying at the school recruited into the navy; Jachmann came aboard the ship in 1844 while it was made available to the school for training purposes. During a training cruise that lasted from June to October 1845, Jachmann held one of the officer positions aboard the vessel, but he had not been officially promoted to officer rank. The cruise went into the Atlantic Ocean and into the Mediterranean Sea, and included stops in London, Genoa, Algiers, Madiera, and Portsmouth. Another Mediterranean cruise followed in July 1846; Jachmann served as the ship's executive officer, second in command to the captain, Jan Schröder, a Dutch officer who had been hired to provide naval expertise. On 27 May 1847, he was formally promoted to second lieutenant. A fourth training cruise followed four days later, lasting until October. On their return, Jachmann and the other officers were sent to winter quarters in Danzig. In November 1848, during the Revolutions of 1848 and the concurrent First Schleswig War against Denmark, Schröder was promoted and Jachmann succeeded him as Amazones commander. Jachmann was promoted to first lieutenant on 29 March 1849. He took Amazone to Stettin for operations against the Danish fleet. She saw no action, however, as the Danes focused their attention on the larger Reichsflotte (Imperial Fleet) in Bremen. On 15 July 1850, the Danish blockade fleet entered Swinemünde and seized several Prussian vessels; Jachmann did not sortie to recapture the vessels, which cast suspicion on him and nearly cost him his command. Amazone, of only , was too weak to challenge the Danish and the only other Prussian vessels in the area were small gunboats of even lesser value as warships. As a result, Jachmann was exonerated. Through the 1850s, Jachmann held a variety of roles. He served as the executive officer aboard the frigate , again as the commander of Amazone, and as the shipyard director at the Königliche Werft (Royal Shipyard) in Danzig. During this period, Jachmann commanded a flotilla of ten gunboats during exercises in July and