Conversation so far:
What happened around the 1910s with Mihail Sadoveanu?
Mihail Sadoveanu became a professional writer in 1908-1909, after joining the Romanian Writers' Society, and becoming its President in September of that year.
What else was Mihail Sadoveanu appointed to besides President of the Romanian Writer's Society?
In 1910, Mihail Sadoveanu was appointed head of the National Theater Iași, a position which he filled until 1919.
What was Mihail Sadoveanu's greatest achievement during the 1910s and World War I?
One of the most prolific Romanian-language writers, Mihail Sadoveanu is remembered mostly for his historical and adventure novels, as well as for his nature writing.

Question: who did he work with?
Self-contained rewrite: Who did Mihail Sadoveanu work with during the 1910s and World War I?