History of Smoke
"… taking advantage of natural cover or darkness to
surprise the enemy or to conceal the direction of an attack,
was fundamental knowledge, even among savages."
Macbeth, William Shakespeare
Using both man-made and natural elements to shield friendly forces is a practice
long regarded as one that could potentially provide the attacker with an
element of surprise. In Macbeth, we also see an example of the use of
obscurants as a means of deception. As forces advance through Birnan Wood to
Dunsinance, their instructions are to:
"Let every soldier hew him down a bough and bear it before him,
thereby shall we shadow the number of our host, and make discovery err in report
of us."
The concept of military smoke screening dates back hundreds of years. One of the
earliest documented uses of smoke screen in combat was the burning of green
vegetation by the Romans and later the burning of peat moss by the Vikings. In
the American Civil War, General Robert Schenck burned wet tree limbs and leaves
to create a smoke screen to cover his retreat. In all of these early smoke
screen attempts, the method employed was direct flame contact with combustible
material.
These combustion methods were a bit uncontrollable and had only limited
advantages in combat. Generally, they could only be used to conceal troop
numbers or to cover a retreat but could not effectively be used in covering
troop advances due to the effect of smoke on the advancing troops. In addition,
because smoke is lighter than air, the smoke cover was only temporary and large
volumes of smoke were necessary to create sufficient cover. Thus a sizable
amount of time was required to ignite and burn the material.
World War II, Britain
British forces used large area smoke screens to protect their towns, cities and
industrial centres from the German Bombing during 1940 / 1941.
British military leaders realized they could not fend off the massive attacks of
the Germans but learned they could protect their assets by hiding them from the
German bombers. Prior to 1941, German bombing campaigns were very effective
against British cities. Reacting to lessons learned from the past, British
forces were familiar with the concept of large area smoke screening. Twenty
years earlier, during World War I, the British successfully used smoke and
obscurants to conceal their own operations during the Battle of Jutland.
Massive German bombing campaigns would have devastated the British forces, and
the British knew they had to take measures to conceal their most vital assets
with visual obscuration. One method the British used to protect their
industrial centres involved the use of smoke pots and British civilians. Under
the Civilian Defence Program, civilians living near industrial complexes would
come out during alerts and ignite smoke pots pre-positioned in the area. A
massive smoke build up occurred once the pots were ignited, which resulted in
huge smoke clouds covering the industrial centres. The smoke clouds prevented
the German bombers from locating their targets.
America
In the early morning of 7 July 1943 the port, lake, channel, outer harbour and
bay at Bizerte were crowded with US ships concentrated for the impending Allied
invasion of Sicily.
Around 4 a.m. on 7 July, approximately 60 German aircraft launched an attack on
the port areas of Bizerte. Though the attack lasted for more than half an hour,
German airplane pilots could not locate their targets. Just minutes before
German planes descended upon Bizerte, US forces used smoke generators to create
a dense fog over the area. Within the screened area, not one bomb hit its
target, nor was a single ship damaged.
The enemy raid on Bizerte failed primarily because of the blanket of oil smoke
US troops made using the M1 mechanical smoke generator. The M1 generator was
the first mechanical generator used for large area smoke and obscurant
screening by US forces during World War II. While the use of smoke operations
was gaining momentum, the M1 was not even on the drawing boards at the
beginning of the war. The M1 smoke generator was quickly fielded in 1942 to
save lives and equipment for situations such as Bizerte.
Today
The "smoke" created by today's technology is neither a smoke (like the product
of a combustion smoke screen) nor a chemical gas (like the product of a
chemical smoke bomb) but was a vapour of a specially designed oil. This 'Fog
Oil' is atomised in the exhaust duct of a small gas turbine engine using a
specially designed nozzle. Exposed to a temperature of some 600°C the atomised oil evaporates instantly. On exiting the exhaust the oil
condenses into a vapour that provides a long-lasting, ground hugging,
obscuration cloud.
