Nice song, but not exactly a folksong, written - as noted where Sorcha's link takes - by Matvej Blanter (1903-1990) & Mihail Isakovskij (1900-1973). Dates back to the days of WWII and nicely disguised as a love song, but is in fact about a more dangerous Katjusha; the rocket launcher built on a lorry/truck ('Stalin's Organ' as it is known here in Finland).

AKS