Zveno-SPB saw limited but successful combat use on the Eastern Front of World War II. In the opening stages, the Black Sea Fleet Air Force was tasked with destroying industrial targets in Nazi Germany-allied Romania. The most important of these was the King Carol I Bridge over the Danube which carried the Ploieşti-Constanța oil pipeline. After several failed attempts to destroy the heavily protected bridge with conventional bombers, the task was given to the Zveno squadron. As a combat test, it was decided to first attack the Constanţa oil depot. On 26 July 1941, two Zveno-SPB aircraft performed a successful attack on the depot in broad daylight with no losses. The fighters disconnected 40 km (22 NM, 25 mi) from the target and returned to the home airfield under their own power.[4]