The Little Black Book of Field Artillery

Laying the Guns

These same series of acronyms and numbers appear multiple times in the notebook. I had to do some investigation into field artillery basics and history to make sense of these. There are two dimensions in aiming a weapon. The horizontal plane (azimuth) and the vertical plane (elevation). The numbers in the book all pertain to azimuth. Up until the late 1800's if you were an artillery man, you could always see your target (this is called direct fire). At Gettysburg, you could determine your azimuth by looking down the sights of your cannon at your target. World War II howitzers could shoot projectiles many miles at an unseen target (this is called indirect fire). So these numbers in the book are a method for getting four howitzers all aimed down the same target line (the azimuth of fire)

Azimuth is measured in angles. If you stand facing due north and then turn in a full circle, you've rotated 360 degrees. Degrees aren't a precise enough unit of measure to aim a howitzer. The unit of measure used in the United States Field Artillery is the mil, 1/6400 of a circle. These 6400 graduations provide the accuracy required for long range fire. So the numbers in the book are basically angles, measured in mils.

When reaching a new firing position, you would have to "Lay the Guns". Gun laying is a set of actions to align the gun barrel so that it points in the required direction. Each howitzer would have a sight and a method for rotating the gun a set number of mils.

Using the Aiming Circle you sight onto the first howitzer and calculate the angle between the Azimuth of fire and the howitzer. This angle is called the deflection. Then the crew of the howitzer would sight back to the Aiming Circle, and rotate the gun until the angle matched the deflection. When the opposite interior angles match, the lines were parallel. This was done for all four guns.

So I think that's what the acronyms and numbers mean in the book. Orienting Line, Azimuth of Fire, Base Angle and deflections for the four guns (#1,#2,#3,#4) and angle readings in mils.

And that's just the azimuth. Then the elevations would have to be calculated. Lots of variables involved, distance to target, terrain elevations, wind, weather, type of projectile. This was the 1940's with no calculators, computers or GPS. I assume all this was being done with maps, protractors and manual math calculations.

Rounds

The other section which is repeated a few times in the book pertains to the type of rounds and how they should be loaded onto vehicles.

Here are my best guesses.

Types of shells

• HE - High Explosive

• HES - High Explosive Shrapnel

• WP - White Phosphorous

• P - Powder

• HC - Hexachloroethane Smoke

• BE - Base-Ejecting, cluster bomb

Types of vehicles

• M10 - Tank Destroyer

• M21 - Mortar Motor Carriage (type of half track)

• T - Tractor

• 2.5 T - 2.5 ton truck (deuce and a half)