CLASH OF ARMIES 1862S
ources of intelligence in the Civil
War were varied, some traditional
and some innovative. For example,
alongside cavalry reconnaissance came
observation from balloons. Pioneered
by the French in the 1790s, the idea for
balloons was revived in 1861 through
the initiative of an individual enthusiast,
Thaddeus Lowe, who offered his services
to the Union. Interception of written
communications was age-old, but
during the war telegraph-tapping also
became common, increasing the need
for ciphers to make messages secure.
Uncensored newspapers procured
from the enemy lines were a prime
source of information. Journalists often
naively revealed details of movements
and plans, although false articles were
sometimes planted to confuse the
enemy. Mapmaking was an important
intelligence activity when fighting over
uncharted terrain. The Confederates,BEFORE
commanders. Her arrest in August 1861
was an early Civil War success for Allan
Pinkerton’s counterespionage detectives.
Another Confederate spy was Belle
Boyd of Martinsburg, Virginia; she
supplied information to Stonewall
Jackson during his Shenandoah Valley
Campaign in 1862, before being
reported and arrested.
For the Union, Elizabeth Van Lew
ran a successful spy network in the
Confederate capital, Richmond. One of
her most useful contacts was Mary
Bowser, a freed slave, who worked as a
servant for Jefferson Davis’s wife. Both
the Union and Confederacy organizedConfederate cipher reel
This cipher machine captured in Richmond was used by
Confederates to encode messages. It used a matrix of 26
alphabets, shifted one letter for each row, from which a
substitute letter was chosen for each letter of the message.
The cipher was easily cracked by Union code-breakers.fighting mostly on their own soil, could
expect local people to update them on
Union movements. For Northerners,
slaves and former slaves—known
collectively as “black dispatches”—were
a valuable source of information.
Documents found on dead or wounded
enemies, or simply left in a field—as
happened during Lee’s Maryland
campaign—all potentially aided the
opponent’s cause.Passing on information
Secret agents and spies took their place
among this panoply of intelligence
sources. Security was absurdly slack
on both sides: officers gave tours of their
positions to interested strangers and
openly discussed their plans or orders.
Thus, well-connected Washington
socialite Rose O’Neal Greenhow had
easy access to military information
that she passed on to ConfederateEspionage and Intelligence
With Confederate and Union sympathizers not readily distinguishable and security lax, the Civil War
created ideal conditions for espionage to flourish. Yet the availability of information from secret sources
did not necessarily translate into an accurate understanding of enemy dispositions or intentions.
By the mid-19th century, intelligence was
recognized as a crucial element in warfare.
But when the Civil War erupted, neither
side had intelligence organizations.
NAPOLEON’S INFORMATION GATHERING
Civil War generals had studied the Napoleonic
Wars of 1803–15 and were aware of the
importance the French emperor, Napoleon, had
accorded to intelligence. Information gathered
from varied sources—foreign newspapers,
interrogation of prisoners, and secret agents—was
sifted and collated by Napoleon’s general staff
to build a picture of the enemy’s strength,
movements, and intentions. The efforts of the
enemy to gather information were countered by
the use of ciphers for written messages and
secret police to track down enemy spies.
U.S. INTELLIGENCE
America had no such system. The Signal Corps, a
U.S. Army innovation of 1860, was in its infancy.
In the early days of the war, intelligence and
counterintelligence were improvised. Private
detective Allan Pinkerton was a key figure on the
Union side, his agents acting as a proto-secret
service. Virginia governor John Letcher set up a
spy network in Washington, while Virginians
still had free access to the capital.