About the Congress of Soviets held on July 5, 1918, where the leader of left socialist-revolutionaries Maria Spiridonova made a speech and called for breaking off Brest Peace Treaty. After the congress the rebellion of left socialist-revolutionaries started with the murder of German ambassador Mirbach. The presence of the division of Lattish riflemen, which entered the capital, allowed to suppress the rebellion.
Source : www.mosfilm.ru