The Industrial Workers of the World (IWW), a communist front which presented itself as a labor union, orchestrated a general strike in Seattle, Washington, terrorizing the city and holding the ordinary citizens hostage. When the strike ended, many IWW leaders fled to the Soviet Union.
In the years prior to WWII, the Soviet Union made use of enlisted agents, who engaged in espionage by extracting classified information about national security and sending it to Moscow, or by influencing policymakers in their decision-making. The Soviets also used unwitting dupes, usually naive idealists, who might not have been aware of the extent to which they were being manipulated to act in the interests of the international communist conspiracy.
Evidence has emerged that the Soviet Union had large numbers of both employed spies and unsuspecting pawns in the 1930s in the United States. Samples from a long list of names include Philip Keeney, Mary Jane Keeney, Haldore Hanson, Dorothy Kenyon, and one of the most famous spies: Alger Hiss.
Although this era lies more than half a century in the past, historians are still reconstructing the plan of the vast Soviet espionage network which existed inside the United States. The task is huge, and as more evidence comes to light, the work grows. Historians Stan Evans and Herbert Romerstein write:
Of note in this respect, covert by nature and kept that way for decades, was the nonstop backstage warfare that was waged between the opposing forces even as peace in theory prevailed among the nations. Only by degrees have we come to understand the extent of this clandestine combat, and a great deal more is still waiting to be discovered. Even so, with the revelations of recent years we have enough data in hand to sketch the outlines of an astounding tale and fill in specifics about some matters long uncertain or contested.
Successive estimates at the scale of Soviet intelligence activity have proven to be too small. Each disclosure of new data reveals the efforts to undermine the United States government to have been larger than previously thought.
Historians will be processing this information for decades to come, and new troves of documents are probably yet to be discovered.