This is one of the books that won me to 50 plus years of revolutionary activity. The other two were 'History of American Trotskyism,' also by Cannon, and 'The Revolution Betrayed' by Leon Trotsky.
In World War I, Eugene Debs and many other socialists were sent to prison for opposing US imperialism's war (see 'Eugene V. Debs Speaks'). Many of these socialist leaders helped found the new Communist Party. Debs didn't, but he saluted Lenin and Trotsky.
When the next imperialist world slaughter came around, the leaders of the Socialist Workers Party and of the Minneapolis Teamsters were jailed under a new law, but for the same reason. Roosevelt and Teamsters president Daniel J. Tobin wanted to eliminate antiwar opposition, especially in the labor movement. So did the Stalinized Communist Party, which backed the war all the way--supporting the no-strike pledge and aiding the attempt to break strikes, supporting herding Japanese-Americans into concentration camps, telling Blacks to moderate their demands and accept serving in a Jim Crow army. And aiding the US government's prosecution of the SWP.
Despite all this, unions representing millions of members protested the convictions. This book is the record of James P. Cannon's testimony in the trial, explaining what fascism is and how to fight it, explaining Stalinism, and explaining that all the Marxists were demanding was the right to express their views, a right supposedly granted by the First Amendment. This is one of the best short expositions of Marxist principles you can find, as well as a primer on how to defend democratic rights.
To understand the background to this trial, Farrell Dobbs' 4-volume set on the SWP revolutionary activity in the Teamsters in Minneapolis and across the Midwest where Dobbs was a Teamster organizer. The last volume of this set, 'Teamster Bureaucracy' is the one that really sets the stage for these events. Also useful is 'The Socialist Workers Pary in World War II' and 'Fighting Racism in World War II.'
For those who are foolish enough to applaud the indictments against Donald Trump, as Leon Trotsky forcefully reminded us in 1939, “Under conditions of the bourgeois regime, all suppression of political rights and freedom, no matter whom they are directed against in the beginning, in the end inevitably bear down upon the working class, particularly its most advanced elements. That is a law of history.”
This sixth edition is by far the best with numerous photos and other illustrations. Don't miss it.