[5] He continued to publish numerous books and articles, helping popularize the idea that a "clash of civilizations" between the East and West was inevitable, and that Japan was destined to be the liberator and protector of Asia against the United States and other Western nations.

Later that year articles by Anagarika Dharmapala and Maulavi Barkatullah appeared in the magazine Michi, published by Dōkai, a religious organization in which Ōkawa was later to play a prominent part.

In the 1920s, he became an instructor of history and colonial policy at Takushoku University, where he was also active in the creation of anti-capitalist and nationalist student groups.

Ōkawa hailed the movements started by Mahatma Gandhi in India and Mustafa Kemal in Turkey as new types of Asian revival.

[4] In 1926, Ōkawa published his most influential work: Japan and the Way of the Japanese (Nihon oyobi Nihonjin no michi), which was so popular that it was reprinted 46 times by the end of World War II.

He continued to publish numerous books and articles, helping popularize the idea that a "clash of civilizations" between the East and West was inevitable, and that Japan was destined to be the liberator and protector of Asia against the United States and other Western nations.

During the March Incident, Ōkawa was a leader in attempting to foment a riot outside the Diet Building in Tokyo, which was intended to initiate the coup.

When the riot failed to occur, Ōkawa wrote a letter to General Kazushige Ugaki explaining the plot and asking for his cooperation.

[5] Released after only two years, he briefly re-joined the South Manchurian Railway Company before accepting a post as a professor at Hosei University in 1939.

[4] In pre-trial hearings, Ōkawa said that his 1924 writings were merely a translation and commentary on Vladimir Solovyov's geopolitical philosophy, and "did not necessarily constitute a plan for a Japanese attack".

[4] During the trial, Ōkawa behaved erratically, including dressing in pajamas, sitting barefoot, and slapping the head of former prime minister Hideki Tōjō while shouting in German "Inder!