Praise for Trading from Your Gut

Roman Tactical Lessons
You can learn some lessons about ways to reduce the pressure
on decision making from the tactics of the Roman army.
The Roman legions were generally arrayed in four lines: the first
in one solid line and the second through fourth in groups known as
maniples. Each maniple was composed of two centuries each of
about 80 men (originally 100 men, which is where we get the Eng-
lish word “century”). 
The first line was comprised of lightly-armored javelin throwers,
known as velites. The other three manipular lines would be com-
prised of standard Roman heavy infantry each equipped with a
shield and a short heavy thrusting sword, known as a gladius. Unlike
the typical enemy that had solid lines, once the velites had retreated,
the Roman legions had regular gaps in each line like a checkerboard
so the second line backed up the gaps in the first line, and the third
line backed up the gaps in the second line. These gaps gave the
legions great flexibility in their maneuvering.
172
T
RADING FROM
Y
OUR
G
UT
From the Library of Daniel Johnson

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ptg
To start the attack, the first line, the velites, would throw their
javelins at the enemy and then retreat through the gaps in the first
regular infantry line. The rear half of each maniple of the second
line of regular centurions would move sideways and forward to fill
the gaps in the lines, and then the entire line would attack the
enemy in a solid unbroken line. The front line would continue fight-
ing until tired, at which point, the third line would move forward to
relieve the second line. These two lines would alternate between
resting and fighting.
The fourth line was generally held as a strategic reserve that was
available to support weak spots in the line or to reinforce the flanks
if there was an attack there. This strategic reserve kept the com-
mander from over-committing to any one decision.
The tactical flexibility and maneuverability of the legions
allowed the commanders to move troops around to respond to unex-
pected challenges on the battlefield. It also allowed commanders to
reinforce positions opposite weak points in the enemy lines with
fresh shock troops who were more likely to be able to break through
and rout the enemy. By applying these reserves at various points
throughout the battle, a commander could experiment to probe for
weakness while maintaining a safe level of reserve capability in case
of weakness in his own lines.
Finally, the tactical flexibility of the legions and their highly dis-
ciplined troops allowed the roman generals to build contingency
plans because they knew they could move men around in response
to threats as they developed. This meant that early mistakes in their
decisions could be corrected in time to prevent a loss of the battle.
A
FTERWORD
• O
N
R
OME
, F
ISHING
,
AND THE
U
PSIDE OF
“G
UT
”
173
From the Library of Daniel Johnson

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ptg
Because any mistakes from early decisions could be corrected
due to the tactical flexibility of the formation, the discipline of the
troops, and the availability of a strategic reserve, Roman command-
ing generals could be more decisive without endangering their suc-
cess. This, in turn, allowed them to seize the opportunity when it
presented itself.