Born Hans Ludwig Raimund Koester in 1844 in Schwerin, Mecklenburg-Schwerin, he entered the Prussian Navy as a Kadettenanwärter (Cadet candidate) on 21 June 1859. He had an active seagoing career in the service, which became the Norddeutsche Bundesmarine in 1866, and then the Kaiserliche Marine (Imperial Navy) in 1871. His first command was the naval brig Undine, which he took on a 15-month voyage to North, Central and South America in 1874-75. In 1887 he was named commander of the Panzerfregatte (armored frigate - later armored cruiser) König Wilhelm, long the largest ship in the fleet.