This is the sto­ry of Richard Rothman’s search to under­stand the force that was so pow­er­ful as to impel his two mater­nal grand­fa­thers, Rubin (Ruby) Schechter and Har­ry Nobel — both raised to be Ortho­dox Jew­ish schol­ars — to vol­un­teer in 1937 to serve in the Abra­ham Lin­coln Brigade and risk their lives in the Span­ish Civ­il War. Under­stand­ing bet­ter than most the ter­rors of fas­cism as they wit­nessed Hitler’s rise in Ger­many, about one-third of the Lin­coln Brigade vol­un­teers were Jew­ish. The book is based on extra­or­di­nary let­ters writ­ten by Ruby, who was killed in Spain, that had been miss­ing for 50 years. For Rothman’s oth­er grand­fa­ther, Har­ry Nobel, and oth­ers who lived on after Ruby, the book explores the force that was so pow­er­ful as to bind them and oth­er intel­li­gent Jews to the US Com­mu­nist Par­ty for two decades until the Par­ty implod­ed in 1956. As we wit­ness events in Ukraine, this chap­ter in his­to­ry, and the lessons of the Span­ish Civ­il War, have new relevance.