“PM had reason to believe (Hitler) will use gas on the Russian Front. (en clair BBC broadcast) No.10 will issue an immediate warning of retaliation” UK War Cabinet Minutes W.M(43)57,21/4/43. Hitler was deterred, accepting UK would hazard London in support of the Ally.
711,000 mustard gas bombs were at Bowes Moor, Yorks, Mkt. Rasen/Norton Disney,Lincs, Lord’s Bridge,Cambs for D-Day for a Light Bomber Wing (88 Sqdn./Boston,107 Sqdn./Mosquito, 226 Sqdn/Mitchell, Swanton Morley) and 15 Sqdn/Mildenhall,Lancaster, 148 Sqdn/Methwold, 214 Sqdn/Chedburgh,Stirling. 10,000 were held till 1956. B.B.Halpenny,Action Stns 2,PSL,83. G.Carter/B.Balmer,P300, R.Bud/P.Gummett,Cold War Hot Science,Harwood,1999. J.Lewis,Changing Direction, Cass,2003 denies suggestions of UK policy of 1st. (not retaliatory, 2nd.strike) use of its 500,000 anthrax bombs v.Germany; he states Staff judged BW as physically unuseable.
Churchill determined Allied policy on all this, not FDR: UK, not DC, would have been the target of retaliation.