; ▁running ▁entirely ▁along ▁the ▁Ar as ▁river , ▁it ▁is ▁the ▁short est ▁border ▁for ▁both ▁countries . ▁ ▁Geography ▁ ▁The ▁Ar as ▁river ▁marks ▁the ▁border ▁for ▁its ▁entire ▁length . ▁The ▁land ▁in ▁the ▁immediate ▁vic inity ▁is ▁flat ▁and ▁und e velop ed , ▁with ▁the ▁exception ▁of ▁a ▁four - lane ▁highway ▁and ▁two ▁custom s ▁check points . ▁The ▁nearest ▁settlement ▁is ▁the ▁village ▁of ▁S ə d ə r ə k , ▁located ▁approximately ▁ ▁east ▁on ▁the ▁A zer ba ij ani ▁side , ▁while ▁the ▁nearest ▁settlement ▁on ▁the ▁Turkish ▁side ▁is ▁the ▁village ▁of ▁Ar al ı k , ▁located ▁approximately ▁ ▁north west . ▁ ▁History ▁ ▁During ▁the ▁ 1 9 th ▁the ▁C au cas us ▁region ▁was ▁cont ested ▁between ▁the ▁decl ining ▁Ott oman ▁Empire , ▁Pers ia ▁and ▁Russia , ▁which ▁was ▁expand ing ▁south wards . ▁Russia ▁had ▁conquer ed ▁most ▁of ▁Pers ia ' s ▁C au cas ian ▁lands ▁by ▁ 1 8 2 8 ▁and ▁then ▁turned ▁its ▁attention ▁to ▁the ▁Ott oman ▁Empire . ▁With ▁the ▁ 1 8 2 9 ▁Tre aty ▁of ▁Ad rian ople ▁( ending ▁the ▁Rus so - T urk ish ▁War ▁of ▁ 1 8 2 8 - 2 9 ), ▁by ▁which ▁Russia ▁gained ▁most ▁of ▁modern ▁Georgia , ▁the ▁Ott om ans ▁recogn ised ▁Russian ▁su zer ain ty ▁over ▁Eastern ▁Armen ia . ▁ ▁By ▁the ▁Tre aty ▁of ▁San ▁Stef ano