He was the son of journalist and poet Julius Krohn, and his sisters were Finnish authors Aune, Helmi and Aino Kallas.

[3] In 1918, Krohn published Kalevalankysymyksia (Kalevala Questions), a two-volume handbook designed for students of Finnish folk poetry.

Krohn had previously argued that the Kalevala evolved from small "poetic germ cells" that merged to form a heroic epic.

While Krohn attributed his change in opinion to his further analysis of "observed facts," he also admitted the influence of the political climate that had emerged following Russification and the Finnish Declaration of Independence.

Writing for the nationalist paper Uusi Suomi in defense of his new position, Krohn stated that "The formerly peaceful nation of Finland has become militaristic [...] Kalevala scholarship has followed the same road.

"[4] Eight years later, he reworked the book for a foreign audience, added folktale examples and published it as Die folkloristiche Arbeitsmethode (Folklore Methodology), which since that time has served as the standard reference work for the Finnish Method.