Three Polish Army soldiers who fell in battle against Soviet troops in the second half of September 1939 are buried in the cemetery. It is not known exactly what the circumstances of their deaths were. It has been established that they were one lieutenant and two second lieutenants. Their bodies were found by Aleksander Trusiuk in the meadows behind the village of Rivne and brought to Ostrówki. The burial was carried out by the villagers without the participation of a priest, as the priest Telesfor Perehuda left the village after the Soviet invasion. In 2005, through the efforts and at the expense of the Council for the Protection of Struggle and Martyrdom Remembrance, a monument was erected on the soldiers' grave. It consists of three elements - an irregular stone in the shape of the date "1939", a simple cross without inscription and a square boulder with the inscription: "Here rest 3 unknown soldiers of the Polish Army fallen in September 1939 / Honour their memory / Government of the Republic of Poland and Compatriots / 2005". Below this is the same inscription in Ukrainian.