New facts have emerged regarding the clandestine activities of Sanzo Nosaka, a controversial Japanese Communist Party leader who was expelled by his party in 1992 and died seven years ago aged 101.

New evidence unearthed in Russia is expected to give historians a fresh perspective on Nosaka's underground life in the United States after he sneaked into the country in 1934 as an agent for Comintern -- the international communist organization headed by Soviet ruler Joseph Stalin.

According to three coded letters Nosaka sent from New York to his Comintern handlers in Moscow in 1934 and now preserved at Russia's National Archives, Nosaka did more than produce antiwar propaganda during his four-year stay in the U.S., as is generally believed by Japanese historians.