Petri became a professor at the Irkutsk State University and taught about the ancient history of the, Indigenous peoples of Siberia.

He documented the cultures of several reindeer herding societies across the East Siberian taiga for Institute of the Peoples of the North throughout the 1920s and 1930s.

The Swedish Lutheran figure Olaus Petri was a paternal ancestor whose descendants later relocated to Livonia in contemporary Cēsis, Latvia.

Imperial Russian authorities had sentenced Bernhard's father, Edward Petri, to internal exile for vague association with the revolutionary Land and Liberty.

He developed a keen interest in anthropology, archeology, and ethnography as he felt the disciplines could combine to reconstruct the ancient material and spiritual cultures of contemporary societies.

In 1912 the Russian Committee for the Study of Central and East Asia directed Petri to head an expedition to Lake Baikal to document the Buryat material, religious, and social culture.

He interviewed members of the Alar, Balagan, Kudin, and Verkholensk Buryat groups; developing an interest in the initiation rites for their shamans in the process.

The Neolithic site Ulan-Khada (Russian: Улан-Хада) was discovered near contemporary Kurkut but wasn't excavated that year.

Irkutsk attracted other academics from Kazan, Omsk, Perm, and Tomsk escaping the Siberian frontlines of the Russian Civil War.

[12] Despite the ongoing conflict the White government Minister of Education Vasily V. Sapozhnikov opened the Irkutsk State University in November 1918.

Many future academics presented their findings in the paper, including Georgy Debets, Mikhail M. Gerasimov, Pavel P. Khoroshikh (Russian: Павел П. Хороших), Gavriil Ksenofontov, Alexey Okladnikov, Vasily I. Podgorbunsky (Russian: Василий И. Подгорбунский), and Georgy P. Sosnovsky[13] At the Irkutsk city museum, Petri became acquainted with the elderly Mikhail Pavlovich Ovchinnikov.

Locally produced watercraft made from Larix sibirica was then used to reach the sites to perform archaeological surveys.

The Sayan Mountains had several related cultures that traditionally practiced reindeer herding; the Dukha in the Mongolian People's Republic, the Tozhu Tuvans of the Tuvan People's Republic, and the Soyots and the Tofalar of the Soviet Union, located in the Buryat ASSR and the Irkutsk Oblast respectively.

The other two herds accounted for only a quarter of the total reindeer; combined they had 203 yaks and Mongolian cattle, along with 73 goats and sheep.

Petri relied on the kulak elite and objectively supported the Soyot's wrong sentiment to secede from the Bourrepublic, to trade freely with Uryankhai and Mongolia, to sell their furs wherever they liked, to get rid of the Communists - these were essentially kulak demands…"[26]Petri continued to study other Siberian Indigenous.

[27] In 1930 an expedition was organized to reach the Evenks that inhabited the Kalakan, Kalar, and Karenga tributaries of the Vitim River.

It was located in an archive containing the inventory of Northern Asia (Russian: Северная Азия, a scholarly journal in the early USSR.

In May he was charged with conspiring with a "German-Japanese fascist... right-wing Trotskyite organization in eastern Siberia" into provoking a revolt in the Buryat ASSR against the Soviet Union.

They collectively studied such topics as settlement patterns of various Siberian ethnicities, the reconstruction of ancient social systems, and the ethnogenesis of certain societies.