In the invasion of Poland 1939, the RWD 8s were used in 13 liaison flights, three aircraft in each, assigned to Armies. Many other aircraft were mobilized during the campaign and used in improvised liaison units. An advantage of the RWD 8 was its capability for short take off and landing on unprepared fields, but the missions of their crews were dangerous. RWD 8s of the Polesie Operational Group were the last Polish aircraft in the sky during the campaign. They were flying reconnaissance missions during the Battle of Kock, and even threw hand grenades.