Although one can take it for granted that the Philadelphia Nazis were not particularly nice people, in the U.S.A. even the Nazis are supposed to be exempt from having a 16-pound bomb designed to maim and kill planted and detonated in their rented clubhouse. 

I don't know if anyone was ever arrested for this. Given the extent of Soviet espionage and subversion in the United States during the 30s, 40s, and 50s, and the fact that 12,000 attended a rally at Convention Hall in Philadelphia a few days before the bombing, the blame for this probably can be laid at the feet of the local Communist Party, which took its direction  from Comintern in Moscow. 

 HAVE FUN, and do e-mail me with comments, questions, corrections, and such! 

Phil Cohen
November 12, 2012