Why is August Strindberg considered a forerunner of Expressionist drama?

August Strindberg is considered a forerunner of Expressionist drama primarily due to the evolution of his dramatic style in his later works, which moved away from the strict Naturalism of his earlier plays.21

Following a period of intense personal crisis between 1894 and 1897, Strindberg’s dramatic form shifted toward dream visions and confessional monodramas. In these plays, such as A Dream Play (1902) and The Ghost Sonata (1907), he adopted a subjective perspective where the entire narrative is filtered through the eyes of a single protagonist.12

This approach, along with his use of stereotyped characters—such as "the Son" or "the Stranger"—directly influenced later Expressionist dramatists. By breaking with the conventions of continuous narrative and surface reality, Strindberg provided a foundation for the Expressionist movement to explore the internal states of mind and fragmented consciousness that became hallmarks of the genre.13