In 1859-1862 he took part in the expedition to the Far East along with Karl Eduard Heusner whom he would follow years later as Secretary of the German Imperial Naval Office.

Between 1874 and 1881 in the Central Division (Zentralabteilung) of the Admiralty, he commanded the cadet ships Undine and Medusa from 1876 to 1878, and then captained the academy corvette Elisabeth of the Arcona class on its global tour from 1881 to 1883, the year the Krakatoa volcano erupted.

Now a Rear Admiral, Hollmann commanded the squadron which accompanied the Kaiser and Kaiserin on their royal visit to Greece and Turkey, 1889 to 1890.

On 22 April 1890, Hollmann became a member of the Federal Council (Bundesrat, upper house of the Parliament) and State Secretary of the German Imperial Naval Office (Reichsmarineamt) in the cabinet of Chancellor Leo von Caprivi, following the resignation of Karl Eduard Heusner.

[4] Nevertheless, when the Kaiser demanded that the navy take territory on the Shandong peninsula in September 1895, he demurred because of the uncertain reaction of Japan, Britain and Russia.

[5] In the struggle over the Kaiser's naval expenditures, he admitted in February 1896 that "there are not 10 people in the Reichstag in favor of our great future fleet plans.