To those that have experienced the "Knife Hand", something that is uniquely American Military, I know the crayon eating group A.K.A. the U.S.M.C. say that they invented the Knife Hand, but they are trying to "culturally appropriate" the Knife hand from the grand daddy of all the services, the U.S. Army. I and many others have experienced the "Knife Hand" first hand in Basic, it is a time honored tradition passed down from the mist of time like the lore of Old. The Knife Hand. I shamelessly cribbed the article from "Angry Staff Officer".
There are many iconic images in U.S. military history: Washington
crossing the Delaware, the surrender at Appomattox, troops landing on
Omaha Beach, to name a few. But few paintings or photographs have
managed to capture one of the most significant weapons in the U.S.
arsenal: the knife hand.

Army
Reserve drill sergeant, Staff Sgt. Robin Brown of Belton, S.C., with
Company C, 1st Bn., 518th Inf. Reg., 98th Training Div. (IET), uses a
demonstrator to teach the proper way to do several basic movements to
Clemson University Reserve Officer Training Corps cadets during a drill
and ceremony lab conducted by drill sergeants of the division on
Clemson’s Bowman Field, Sept. 3, 2015. (U.S. Army photo by Sgt. Ken
Scar) (Photo Credit: Sgt. Ken Scar)
Able to cleave the air with a thunderous blast of justice while
projecting command aura, the knife hand serves as one of the single most
effective weapons for modern U.S. military leaders. Indeed, new
recruits into the U.S. military are greeted by knife hand-wielding drill
sergeants, inspiring fear, respect, and awe. The knife hand can be used
to discipline wayward troops, drive a point home during a briefing, or
to direct the firepower of America’s finest in combat. It is no stretch
of the English language to say that the knife hand has done more for the
U.S. military than when they started putting the Skittles packets in
MREs. But where did this monumental motion come from?
The origins of the military knife hand are shrouded in mystery and
legend. As with all important facets of history, scholars are divided on
the subject. Some say that it dates from the American Civil War. In its
original form, the knife hand was known as the
doigt de guerre,
seen in the image below, in a historical recreation of that gesture
employed by Capt. Canastadus Rufudus of the First Georgia Fusiliers
(light). This gesture was inherited from the French military tradition.

Author Emo Mutz’s recreation of the doigt de guerre.
Unfortunately, the
doigt de guerre proved difficult to see in the era of black-powder musketry, so the revised
System of Infantry Tactics
by Brig. Gen. Silas Casey established the knife hand in its current
form, as noted in “Title Fourth, School of the Battalion Part First,
Article Third,
couteau à main:
“The hand, dexter, shall be formed as of a plane, inclined so the
distal side of the hand is perpendicular to the ground. The hand shall
be raised smartly to an angle of 45 degrees and, through rapid vigourous
motion, be brought down in a series of strokes viz a trebuchet.”
The
couteau à main was quickly adopted by the Federal Army who
had, without the benefit of the knife hand, gone through a rapid
succession of commanding generals before Lt. Gen. Grant’s staff
implemented it as a means of communicating orders. Grant would often
keep his knife hand holstered at the ready as seen in the below
photograph, using a popular military pose as a sheath for his deadly
weapon. This procedure was widely adopted as can be seen in many
surviving images of Civil War Soldiers to this day.

Knife hand, holstered.
However, some scholars believe that the knife hand comes to the U.S.
military from the Prussian tradition. It was during the Seven Years War
that a young Second Lieutenant Friedrich Wilhelm von Steuben first used
the
messerhand to direct his troops during the Battle of Prague.
Some say that his time as aide-de-camp to Frederick the Great further
enforced his belief that the use of the
messerhand could be used
not only in combat, but in instruction as well. In 1777, when von
Steuben – now bearing the title of “Baron” – arrived in the United
States, he brought his theory of the
messerhand with him.
During the grim winter at Valley Forge, Baron von Steuben began a
training regimen for the Soldiers of the Continental Line. Often
frustrated by the language barrier, von Steuben would demand for someone
to translate his profanity into English. However, the Prussian officer
did find one thing that exceeded the bounds of simple language: the
knife hand.
As we read in a letter from a young Pennsylvanian officer in 1778,
“Brite and early today, We stood to for Drill, the Colde pierced my
Bones, but then we did see the Prussian noble, and unleasheth he a
Mighty Hand, borne aloft with a Precise and Dread Purpose. Even as unto
the Maker shall I never forget the swift Fury and Exactness with which
he did upbraid us, as the way the Creator of the Universe set all in His
Image. Strange to tell, my feeling of chill vanished away when his Hand
did stab in my face and all was replaced with a Fierce and Fiery
feeling of Awe.”
Because of von Steuben’s regimen of training – as well as the knife
hand that he had empowered them with – the Continental Army was able to
go into battle in 1778 equipped with the tools needed to stand
toe-to-toe with the British Redcoats. Because of the knife hand,
American gained its independence from England. From then on, the knife
hand entered into unwritten U.S. military doctrine.

Two
Soldiers in the background can be seen attempting to brandish the knife
hand at the Battle of Monmouth, 1778. It is possible that von Steuben’s
technique may have been too difficult to grasp. Fortunately, Molly
Pitcher knew what she was doing.
Of course, the knife hand could have merely developed out of the
habitual need to brandish something. And since officers and
non-commissioned officers may no longer use a sword, saber, riding crop,
or
spontoon to point at things, the knife hand has rapidly come into vogue, a pattern beginning after World War II.
Whatever its origins, the knife-hand has left its imprint on the U.S. military. Its use has come under some criticism
lately,
as being too harsh. However, used at the correct time and place, the
knife hand is still a crucial weapon, whether on the battlefield under
fire or when keeping colonels awake during a 3 hour staff meeting. The
knife hand: don’t leave home without it.