Complex sentence: Later Soviet authors would claim central responsibility for these actions, however, including Yaroslavsky (who was a participant in these killings) who justified the campaign by claiming that the church was fighting against them.
Split into simpler sentences: Later Soviet authors would claim central responsibility for these actions, however. One of these later authors was Yaroslavsky (who was a participant in these killings) who justified the campaign by claiming that the church was fighting against them.