Am'Ap°riT/  ?9hi8!m'  }         Methods  of  Gas  Warfare. 
263 
The  element  of  surprise  came  in  an  attack  by  night.  The 
meteorological  conditions  are  much  better  at  night  than  during  the 
day.  The  best  two  hours  out  of  the  twenty- four,  when  steady  and 
downward  currents  exist,  are  the  hour  between  sunset  and  dark 
and  the  hour  between  dawn  and  sunrise.  Gas  attacks  have  there- 
fore been  frequently  made  just  in  the  gloaming  or  early  morning, 
between  lights.  This  took  away  one  of  the  easy  methods  of  spot- 
ting gas,  that  of  seeing  it,  and  we  had  to  depend  upon  the  hissing 
noises  made  by  the  escaping  gas,  and  upon  the  sense  of  smell. 
Another  element  of  surprise  was  the  sending  out  of  more  than 
one  cloud  in  an  attack.  After  the  first  cloud  the  men  would  think 
it  was  all  over,  but  ten  minutes  or  half  an  hour  later  there  would 
come  another  cloud  on  exactly  the  same  front.  These  tactics  were 
very  successful  in  at  least  one  case,  namely,  the  attack  near  Hulluch 
in  1916.  Some  of  the  troops  discarded  their  helmets  after  the  first 
wave  and  were  caught  on  the  second,  which  was  very  much  stronger 
than  the  first. 
Efforts  were  also  made  to  effect  surprise  by  silencing  the  gas. 
But  silencers  reduced  the  rate  of  escape  so  greatly  that  the  loss  of 
efficiency  from  low  concentration  more  than  made  up  for  the  gain 
in  suddenness.  Another  method  was  to  mix  the  gas  up  with  smoke, 
or  to  alternate  gas  and  smoke,  so  that  it  would  be  difficult  to  tell 
where  the  gas  began  and  the  smoke  ended. 
The  last  attack  made  on  the  British  by  this  means  was  in  Au- 
gust, 1916.  Since  that  time  the  Germans  have  used  gas  three  times 
on  the  West  Front  against  the  French,  and  have  also  used  it  against 
the  Italians  and  the  Russians.  It  has  been  practically  given  up 
against  the  British,  although  the  method  is  by  no  means  dead. 
The  last  attack  was  a  slight  set-back  in  the  progress  of  gas  de- 
fense. The  casualties  had  been  brought  down  to  a  minimum,  and, 
as  shown  by  the  fact  that  the  percentage  of  deaths  was  high,  pro- 
tection was  complete  in  all  cases  where  used,  casualties  being  due 
to  unpreparedness  in  some  form.  The  attack  in  question  was 
brought  on  under  difficult  conditions  for  the  defenders,  as  it  was 
made  on  new  troops  during  a  relief  when  twice  as  many  men  were 
in  the  trenches  as  normally.  Furthermore,  they  had  to  wear  hel- 
mets while  carrying  their  complete  outfit  for  the  relief.  This  was 
the  second  time  the  Germans  caught  us  in  a  relief,  whether  through 
information  or  luck  we  cannot  say. 
The  protection  that  had  been  devised  against  phosgene  proved 
