Katyusha

Katyusha, a Russian folk song about a girl named Katyusha waiting for her lover to return from fighting in a war. In a way, it's a Russian version of Muss Denn which is a German folk song that is about a wayfarer saying goodbye to his lover and vows to marry her when he returns as he tells her not to be sad. Both songs have been associated with soldiers (even if the singer's occupation in Muss I Denn has been misremembered and misinterpreted as a soldier) in recent years.
At the start of Operation Barbarossa, an industrial school in Moscow held a performance of Katyusha by female students to the soldiers who were about to serve their duty to protect and save the USSR from Nazi Germany. 3 year prior, the song had been performed at the House of Unions by Valentina Batishcheva but it seems to have become popular thanks to Operation Barbarossa's Soviet front as many other singers in the Soviet Union have performed Katyusha like Eduard Khil who is known for his vocalise song "I Am Very Glad, as I'm Finally Returning Back Home"
In fact, Katyusha ended up being so popular that it found its way in other parts of the world:
In Iceland, Katyusha is called Vertu til er vorid kaliar å Pig which translates to z, Be ready when spring car'15" which encourages hard work in the hay fields during springtime.
In France, Israeli singer Rika Zaroni released Casatchok in 1969 which is a French langage take on Katyusha
Speaking of Israelis, the song got a Hebrew dub in 1945 and has been popular in Israel ever since.
Syria's communist party have also sung Katyusha albeit in Arabic.
Italian partisans had Fischa il vento (the Wind blows) which was one of their anthems when Italy switched over to the Allied Side.
Spaniards who were part of the Blue Divsion had (designated by the Germans and the the Spanish Volunteer Division sand a pro Francoisist chant Primavera to the tune of Katyusha.
The Greeks during the Greek Civil War Of 1946-1949 had their own version Of the song called O Üpvog rou EAM (The hymn Of EAM in English).
Even CHINA who was influenced by the USSR in the half of the 20111 century loves this song and there was a time in Chinese history where young Chinese people would regret not being able to
sing Katyusha. The 2015 Moscow Victory Parade had the Chinese honour guard perform Katyusha followed by a performance by the Massed Bands of the Moscow Garrison performing the song
for their former contingents India, Mongolia, Serbia and China.
The campaign song GOYANG Jempol Jokowi Gaspol for Indonesian politician Joko Widodo uses Katyusha's melody.
The Japanese anime Girls und Panzer has this song exclusively in its Japanese dub.
On a non-song related note, the Red Army's BM-8, BM-13 and 3M-31 rocket launchers are nicknamed Katyusha.