It was said about him after his death that "the road which the aged Iwasa walked, extending through the Meiji, Taishō and pre-war and post-war Shōwa eras, was the history of the Japanese anarchist movement itself.

During this period, his ideology developed into anarcho-communism, and he was particularly radicalised by the Russo-Japanese War as many other Japanese anarchists such as Kōtoku Shūsui were.

[11] Compared to the more anarcho-syndicalist views of activists such as Ōsugi, Sakutarō Iwasa was an advocate of anarcho-communism due to his skepticism of labour unions.

Alongside Hatta Shūzō, he was one of the key advocates of what was labelled 'pure anarchism', so-called due to its opposition to 'contamination' by Marxist ideas.

[14] In 1927, Iwasa published his book titled Anarchists Answer Like This, which criticised the idea of class struggle, and provoked the division between these two factions.

[15] The split was affirmed in 1928 when, at the second conference of Zenkoku Jiren, anarcho-syndicalists walked out due to jeering and the antagonistic relationship between the two factions.

[16] Iwasa had been in China from 1927 until November 1929, participating in anarchist struggles in that country such as the Labour University in Shanghai, and so was not directly involved in that division (although his influence did contribute to it).

One way in which he fulfilled this was by hanging placards around his neck to advertise anarchist journals on his long journeys throughout Japan to help organise the Federation.

He was described by other anarchists as having been "held in esteem as high as the mountains and the stars", and even his political opponents such as Yamakawa Kikue noted that he was an 'eternal youth'.

He opposed centralised authority, whether in the attempted 'Anarchist Communist Party', or through syndicalist methods of revolution, resulting in his labelling as a 'pure anarchist'.

This harsh criticism of labour unions was significant in influencing the Japanese anarchist movement away from syndicalist methods.