[2][3] Suzuki moved to the United States in 1919, where he met Sen Katayama and Tsunao Inomata, who were both Leninists.

However, Suzuki became an increasingly prominent target of the government, and he was arrested in 1937 under the Peace Preservation Law as part of the Popular Front Incident.

Later, in his inaugural speech as party chairman, he famously said "Young men, do not take up arms; young women, do not send your husbands and sons to the battlefield" which caused a huge political stir and became a rallying cry of the pacifist movement in Japan, although it was only intended to rebuke Prime Minister Yoshida Shigeru's attempt to secure aid from the United States to rebuild the military of Japan.

After the signing of the San Francisco Peace Treaty in 1951, the Socialist Party split into left and right wings.

Suzuki remained chairman of the left wing, which had only 16 seats in the House of Representatives; in the 1955 elections, it jumped to 89 seats, thanks to support from the General Council of Trade Unions and popular support from a war-weary electorate that largely agreed with the party's principle of unarmed neutrality.

During the 1960s, Suzuki gradually pressed the Socialist Party to the left, but it continued to languish as Japan's economic recovery sped up.