Her play "Watch on the Rhine" opened on Broadway on April 1, 1941, and ran for 378 performances. It won the New York Drama Critics' Circle Award. She wrote the play in 1940, when its call for a united international alliance against Hitler directly contradicted the Communist position at the time, following the Nazi-Soviet Non-Aggression Pact of August 1939. Early in 1942, Hellman accompanied the production to Washington, D.C., for a benefit performance where she spoke with President Roosevelt. Hammett wrote the screenplay for the movie version that appeared in 1943.