Excerpt from Shmerke Kaczerginski’s memoir I Was a Partisan, in which he recalls the birth of this song.

The ghetto buzzed with excitement when over our hidden radio we heard the news flash from the Polish Underground: “Hello! Hello! The remaining Jews in the Warsaw Ghetto have taken up arms against the Nazis. The ghetto is in flames!” Word of the uprising boosted our morale, gave us pride. We grew wings. We brazenly stared at the Nazis-and they soon knew what this look signified. No doubt more than a few were thinking: “Perhaps I’ll have to fight the Jews of Vilna! Perhaps I’ll be killed!” For the evening of May First [1943], we had organized a cultural event, “Springtime in Yiddish Literature.” An innocent name, “Springtime.” But the hundreds who came understood that our real purpose was to celebrate May Day. One speaker, then another. One song, then another. And everything suffused with the spirit of Warsaw. [In the excitement,] I had not noticed Hirsh Glik standing by my side:

What’s new with you, Hirshl?
I've written a new song. Do you want to hear it?
You wrote a song during all this commotion? So, read.
Not now. I'll see you tomorrow.

The next day, Hirsh stopped by quite early. “Listen closely,” he said. He sang quietly at first, but with passion, with heart. His eyes were ablaze. I wondered: Where does he find such unshakable faith? As his voice grew firmer, he began to hammer out the words, stamping his feet as if he were now on the march. I pressed his hand. “Wonderful, Hirshke, wonderful.” Through his words, I felt the impact that the Warsaw Uprising had made on him. Partisan Headquarters soon decided to designate Glik’s song the official hymn of the Underground fighters. But it was not necessary to wait for a decree: the song had already spread throughout the ghetto.

— From I Was a Partisan by Shmerke Kaczerginski