When the legendary actor and civil rights activist Paul Robeson gave a concert in Moscow in 1949, he closed the show with one encore: his rendition in Yiddish of the “Partisan’s Hymn,” the anthem of Jewish resistance fighters.

That stirring and long forgotten moment is the spark of Ben Gonshor’s play, “When Blood Ran Red,” just selected the winner of the National Yiddish Theatre Folksbiene’s David and Clare Rosen Memorial Play Contest, sponsored as part of the NYTF’s centennial celebration. The competition, open to plays in Yiddish and English, was judged by a panel of Tony Award-winning and Broadway playwrights, directors and producers. The drama will be presented in a staged reading as part of the NYTF’s weeklong KulturfestNYC in June.

Gonshor, whose first language is Yiddish, has been performing on the Yiddish stage since he was 5 and joined the Dora Wasserman Yiddish Theatre company in Montreal. He has performed with the DWYT in many productions around the world, and he also wrote the book for “Houdini,” an original musical produced by Montreal’s Segal Centre for the Performing Arts.

In conceiving “When Blood Ran Red,” he was inspired by a radio interview with Paul Robeson Jr. talking about his father’s experience in Moscow. Curious about his choice of the “Partisan’s Hymn,” Gonshor then dug into the history of Robeson’s friendship with Soviet artists like Solomon Mikhoels, artistic director of the Moscow State Jewish Theater. The story became more personal, as Dora Wasserman, who founded what was then called The Yiddish Theatre in Montreal in 1958, had been a student of Mikhoels.

While studying for his M.F.A. at the University of Southern California’s School of Cinematic Arts in the late-1990s, Gonshor wrote a screenplay based on Robeson’s story, but he admits that it was an epic historical saga that spanned continents. His professors said it was beautiful but would never get made.

He then simplified the script and “let the words tell the story.” The play’s opening prologue sets the historical context.

The final round of the Rosen Contest was conducted at the Manhattan Theatre Club Studios, and involved a day of presentations by professional actors of 30-minute excerpts from each of the five remaining plays. The panel of judges, which included producers Emanuel Azenberg and Jane Dubin, playwrights Jon Marans, Israel Horovitz and Jeff Baron, and composer-lyricist Jason Robert Brown, announced its selection after several weeks of deliberation.

For Gonshor, walking along Broadway that day to hear his play being read in front of the blue-ribbon panel was “surreal, already a dream come true. I felt that I won, regardless,” he said in a telephone interview. Nonetheless, he was “ecstatic and incredibly honored” to learn that his play was chosen.

“I’m delighted that this story is going to be told,” he says. “When it comes to Robeson, people don’t understand — I don’t believe there would be a President Obama or a Martin Luther King without people like Robeson who went before them.”

“When Blood Ran Red” is in English, although the “Hymn of the Partisans” is sung in Yiddish. “I don’t know if I could write a play in Yiddish,” Gonshor says. “I don’t have the kind of fluency to write something literary.

“My feeling is that whatever brings people to Yiddish is important — I want to open up all the avenues to allow people to experience that world,” he says. “We can’t close the door and say that only people who speak and understand Yiddish are invited. That’s not the theater.”

Gonshor will also be performing at Kulturfest, playing the lead role in the Dora Wasserman Yiddish Theater’s presentation of “The Dybbuk,” to be directed by Bryna Wasserman, Dora’s daughter, and now NYTS executive producer.