In WWI, after the Germans had taken the Kaunas fortress on August 18,1915 and were anxious to take the communications centre Vilnius by outflanking, the river Nemunas (Njemen) had to be negotiated at several other points as well. At Prienai (Preny), the river was crosssed on August 22 by 31. Infanterie-Division, led by Gen.Ltn. von Berrer. While each German division was accompanied by its mobile Feldpost, no stationary Feldpost was later set up at Prienai.
During the German retreat from Russia at the end of 1918, the Red Army advancing into southern Lithuania stopped at a Russo-German agreed demarcation line some distance east of the river Nemunas. The Soviet strategy to move further west included a directive for the 7th Regiment of the Pskov Division to cross the Nemunas at Prienai, but was thwarted in February by rapid deployment, around Jeznas, of fresh Lithuanian troops and units of the 18th Saxonian Volunteers Regiment. In the first half of 1919 Prienai remained a kind of military transit point, and the home-going 19th Saxonian Volunteer Regiment, in early July, also left from Prienai. While on Lithuanian territory Saxonian volunteers made use of their own Frw.Feldpost 728 stationed in Kaunas.
The first postmaster (įgaliotinis) to open a Lithuanian post office at Prienai was Tamošius Simonaitis appointed as from January 13, 1919 who stayed on at least in 1920 as well. One of the first additional appointees, from July 20, 1919 was valdininkas Pijus Vasylius, a graduate of the recently organised Postal School.
Thus far there has been no evidence of either Vilnius Issues or Kaunas Issues being available at Prienai. The earliest issue noted at Prienai is Second Berlin Issue, followed by the ubiquitous Fourth Berlin Issue, the Sėjėjas Issue etc.
In the absence of a standard postmarker, early cancelling and indeed throughout 1919 was done by manuscript, indicating place and date.
When late in 1919 Prienai was supplied with a registration cachet, it was also used for cancelling.
A standard calendar-type postmarker seems to have been obtained in 1920.
Known provisional markings:
MS cancelling showing place and date:
4 / IV / 19 postcard to Germany, Berlin II 40 [colln.Doniela]
5 / VII / 19 letter to Germany Berlin, IV 20, 30 [colln.Lapas]
various dates 1919, singles, Berlin IV [several collns]
12 / XII / 19 Money Order to Lith. soldier, entered with a registration cachet, Berlin IV 75 [colln. Doniela]
Cancelling by registration cachet:
no date, singles, Berlin IV [several collns]