[1] His parents were Major General Josef Hann von Weyhern (1765–1840) and Christiane Caroline Elisabeth Hermann.

In the same year, Hann von Weyhern became a lieutenant colonel and commander of the 1st Dragoon Regiment in the Schleswig-Holstein Army.

[3][4] In 1852 Hann von Weyhern returned to Prussian service and was employed with a license as major à la suite in the 2nd Dragoon Regiment.

On 17 September 1866 Hann von Weyhern became commander of the 4th Division and three days later promoted to Lieutenant General with the award of the Order of the Crown, 2nd Class with swords.

As head of the 5th Hussar Regiment, which he was from 1872, Hann von Weyhern received the Grand Cross of the Order of the Red Eagle in early September 1873 with oak leaves and swords.