▁Stevens on ▁was ▁t apped ▁to ▁head ▁the ▁Committee ▁on ▁Ali ens ▁of ▁the ▁mayor ▁of ▁New ▁York ' s ▁Committee ▁on ▁National ▁Def ense . ▁This ▁new ▁activity ▁inspired ▁Stevens on ▁to ▁volunte er ▁his ▁services ▁to ▁the ▁U . S . ▁Justice ▁Department ▁in ▁ 1 9 1 7 , ▁assist ing ▁it ▁in ▁its ▁investigation ▁of ▁so - called ▁" G erman ▁propag anda ." ▁Stevens on ▁began ▁creating ▁a ▁card ▁file ▁indexing ▁the ▁names ▁of ▁individuals ▁in ▁the ▁country ▁whom ▁he ▁sus pected ▁of ▁pro - G erman ▁sympath ies ▁and ▁worked ▁in ▁close ▁connection ▁with ▁the ▁War ▁Department ' s ▁Military ▁Int elligence ▁Division , ▁based ▁in ▁New ▁York ▁City . ▁ ▁Stevens on ▁was ▁neither ▁a ▁special ▁agent ▁of ▁the ▁Justice ▁Department ' s ▁Bureau ▁of ▁Investig ation , ▁nor ▁a ▁member ▁of ▁Military ▁Int elligence , ▁but ▁was ▁rather ▁an ▁activ ist ▁who ▁co oper ated ▁with ▁both ▁as ▁a ▁member ▁of ▁the ▁American ▁Prote ct ive ▁League , ▁a ▁non - g overn ment ▁ag ency . ▁On ▁August ▁ 3 1 , ▁ 1 9 1 8 , ▁Stevens on ▁learned ▁the ▁effic acy ▁of ▁the ▁t actic ▁of ▁ra iding ▁one ' s ▁political ▁oppon ents ▁when ▁he ▁and ▁the ▁American ▁Prote ct ive ▁League ▁helped ▁federal ▁agents ▁armed ▁with ▁a ▁search ▁war rant ▁storm ▁the ▁New ▁York ▁headquarters ▁of ▁the ▁National ▁Civil ▁Libert ies ▁Bureau , ▁for er un ner ▁of ▁the ▁American ▁Civil ▁Libert ies ▁Union . ▁Publications , ▁documents ,