▁of ▁the ▁cast or ▁plant . ▁The ▁U . S . ▁conducted ▁tests ▁concerning ▁two ▁methods ▁of ▁ric in ▁dis sem ination : ▁the ▁first , ▁which ▁involved ▁ad her ing ▁the ▁to x in ▁to ▁sh rap nel ▁for ▁delivery ▁by ▁art illery ▁shell , ▁was ▁successful ; ▁the ▁second , ▁deliver ing ▁an ▁a eros ol ▁cloud ▁of ▁ric in , ▁was ▁proven ▁less ▁successful ▁in ▁these ▁tests . ▁Ne ither ▁delivery ▁method ▁was ▁perfect ed ▁before ▁the ▁war ▁in ▁Europe ▁ended . ▁ ▁In ▁the ▁early ▁ 1 9 2 0 s ▁suggestions ▁that ▁the ▁U . S . ▁began ▁a ▁bi ological ▁weapons ▁program ▁were ▁coming ▁from ▁within ▁the ▁Chem ical ▁War fare ▁Service ▁( C WS ). ▁Chief ▁of ▁the ▁C WS , ▁Am os ▁F ries , ▁decided ▁that ▁such ▁a ▁program ▁would ▁not ▁be ▁" prof itable " ▁for ▁the ▁U . S . ▁Japan ' s ▁Sh iro ▁I sh ii ▁began ▁prom oting ▁bi ological ▁weapons ▁during ▁the ▁ 1 9 2 0 s ▁and ▁tou red ▁bi ological ▁research ▁facilities ▁world wide , ▁including ▁in ▁the ▁United ▁States . ▁Though ▁I sh ii ▁concluded ▁that ▁the ▁U . S . ▁was ▁developing ▁a ▁bio - we ap ons ▁programs , ▁he ▁was ▁incorrect . ▁In ▁fact , ▁I sh ii ▁concluded ▁that ▁each ▁major ▁power ▁he ▁visited ▁was ▁developing ▁a ▁bio - we ap ons ▁program . ▁As ▁the ▁inter war ▁period ▁continued , ▁the ▁United ▁States ▁did ▁not ▁emphas ize ▁bi ological