▁and ▁German ▁border lands . ▁Since ▁ 1 5 6 9 , ▁when ▁it ▁was ▁c eded ▁by ▁the ▁Grand ▁Duch y ▁of ▁Lith u ania , ▁during ▁the ▁era ▁of ▁the ▁Polish – L ith uan ian ▁Commonwealth , ▁the ▁territory ▁belonged ▁to ▁the ▁Pod l ask ie ▁Vo iv odes hip ▁and ▁was ▁part ▁of ▁the ▁Kingdom ▁of ▁Poland . ▁However , ▁Se j ny ▁was ▁a ▁property ▁of ▁Domin ican ▁fri ars ▁from ▁Vil nius . ▁ ▁During ▁the ▁ 1 9 th ▁century , ▁the ▁town ▁was ▁part ▁of ▁the ▁Russian - control led ▁Congress ▁Poland . ▁During ▁World ▁War ▁I , ▁the ▁region ▁was ▁captured ▁by ▁the ▁German ▁Empire , ▁which ▁intended ▁to ▁incorpor ate ▁the ▁area ▁into ▁its ▁province ▁of ▁East ▁Pr uss ia . ▁After ▁the ▁German ▁defeat , ▁the ▁vict orious ▁Ent ente ▁was ▁willing ▁to ▁assign ▁the ▁territory ▁to ▁either ▁the ▁newly ▁independent ▁Poland ▁or ▁Lith u ania . ▁The ▁future ▁of ▁the ▁region ▁was ▁discussed ▁at ▁the ▁Paris ▁Peace ▁Conference ▁in ▁January ▁ 1 9 1 9 . ▁The ▁Germ ans , ▁whose ▁former ▁Ober - O st ▁administration ▁was ▁prepar ing ▁to ▁ev acu ate , ▁initially ▁supported ▁leaving ▁the ▁area ▁to ▁a ▁Polish ▁administration . ▁However , ▁as ▁Poland ▁was ▁becoming ▁an ▁al ly ▁of ▁France , ▁German ▁support ▁gradually ▁shift ed ▁towards ▁Lith u ania . ▁In ▁July ▁ 1 9 1 9 , ▁when ▁the ▁German ▁troops ▁began ▁their ▁slow ▁retre at ▁from ▁the ▁area , ▁they ▁deleg ated