In World War One, after the fall of Šiauliai and Panevėžys, Kupiškis (Kupishki, Kupischki) was taken on August 3, 1915 during a major battle (Schlacht bei Kupischki) by 1. Reserve-Division and 78. Reserve-Division advancing respectively on the left and on the right side of the strategic railway line leading to Daugavpils (Dvinsk, Dünaburg).
When the German army withdrew from Russia, Kupiškis was entered by units of so-called International Division of the Red Army in very late December 1918. During the Wars of Independence Kupiškis was taken by Lithuanian forces (Panevėžio grupė) on May 31, 1919
Kupiškis had had a post office in czarist times but was not included in the civilian Postgebiet Ob.-Ost structure, though from March 1917 to December 1918 it did have have a resident Feldpost 390. For the Bolshevik period, Kupiškis (as Kupishki) appears in an archival list of post offices (actual or planned ?) dated March 10, 1919 but there is no surviving tangible evidence of its activity.
As Kupiškis was considered to be of some importance, a mandate to open a Lithuanian post office was given to Juozas Čipkus as early as December 23, 1918. Due to Bolshevik occupation his appointment was annulled on January 15, 1919 but re-confirmed as from June 7, 1919. The following year, as from August 1, 1920, Juozas Čipkus was promoted to Assistant Postmaster at the regional P.O. Ukmergė and was replaced at Kupiškis by Nikola Čereško.
For stamps, Kupiškis was provided with Fourth Berlin Issue, followed by the Sėjėjas Issue etc. At the beginning Kupiškis had no formal postmarker, so cancelling was done in manuscript, indicating date and place or just place. So far, nothing is known about other provisional postal markings.