Maybe you hadn't heard about this war movie before. This a Romanian drama movie set at the end of World War II. His original title is "Portile albastre ale orasului". It was directed by Mircea Muresan, written by Marin Preda, and starred by Romeo Pop, Costel Constantin, Dan Nutu, among other actor. It was released in 1974.
The storyline is as follow. Freshly released from a military hospital where he had been treated for a wound caused by one of his subordinates, 2nd lieutenant Rosu retakes command of his AA battery. As Romania switches sides from the Axis to the Allies in August 1944, his unit fights to protect Bucharest from German bombers and fend off enemy attacks against their position.
On this war movie you can see original German 37 mm Flak used by Romanian Army. In 1938, the Kingdom of Romania acquired the license to locally produce 360 guns, officially known as "Tun antiaerian Rheinmetall calibru 37 mm model 1939" ("37 mm Rheinmetall anti-aircraft cannon model 1939") at the Astra factory in Brașov. By May 1941, 102 had been built, and by October 1942, the production rate was 6 pieces per month.