Smoke can be discharged from _Artillery_ shells, Artillery or
_infantry_ mortar bombs, Infantry rifle grenades, smoke candles,
_Aircraft_ bombs, _Engineers'_ stationary generators, or the exhaust
pipe of _Tanks_. It is used to conceal movement for the purposes of
surprise or for reducing casualties, and can be so employed as to
impose night conditions on the enemy while one's own troops retain the
natural visibility; but while the weight and direction of an intended
blow may thus be hidden from the enemy a warning is given of the time
of its delivery. It is possible, however, to mystify, as well as to
surprise, the enemy by the use of smoke, and its strategical and
tactical value will ensure its adoption in Modern Warfare. In the
closing battles of the Great War "the use of smoke shells for covering
the advance of our infantry and masking the enemy's positions was
introduced and employed with increasing frequency and effect" (Sir D.
Haig's Dispatches).
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