Saturday, June 20, 2009

42 equals the 75mm Gun

After all the work up, we now finally get to the actual artillery piece. The Gun that started the revolution, broke the 1000 year box and made a whole profession go "hmmmmm".

Ladies and Gentlemen, I give you the French 1897 Mle.

An actual, functional French 75mm in action at Fort Sill (photo complements of the author).

A close up picture of the French 75 Mle, slightly modernized with rubber tires for towing with motor vehicles (also from the author).

Okay, so its a cannon. No, its not. This is the FIRST MODERN CANNON ever created. The older black powder weapons had been brought to their evolutionary end in the late 1880s with several changes and developments.

First, we had improvements in metalluragy which had led to new alloys, better steel and therefore stronger guns capable of taking greater pressure and force. Which was great due to the second development which was the development of new chemical propellents which replaced black powder. Black powder was dirty, corrosive and didn't work well in the damp and wet. Several types of new propellent and explosives were developed during this time, the most commonly used being cordite (which we still use). These propellents would have blown older bronze or iron guns apart unless they were built with heavier barrels which in turn meant you couldn't move them. With steel guns, you could use this stuff and still have a mobile gun with the added bonus of increased range, less smoke and greater reliability.

The other two improvements were mechanical in nature. Number three development was the invention of a easy to use and reliable breech loading system. This was called the "Nordenfelt Essentric Screw" and it allowed the use of fixed ammunition (i.e. a shell, its propellent both put together in a brass shell casing). You rotated a lever and moved a solid breech block either down and out of the way to eject and reload a shell, or move the block up and lock the breech closed to fire.

But it was the fourth development that really rocked the artillery's world and was a pure work of the French Army. This was the Long Recoil System (or if you want the technical jargon, a hydro-pneumatic recoil system). Although the original idea had been worked on by Krupp, they were unable to make it work due to leaks of the hydrallic fluid and loss of air pressure. The French hit on the design and assigned several engineering officers to work on it starting in 1892. They fixed the issues by 1896 and started production in 1897. This system allowed something that had never been done before in artillery history and that was the ability to shoot without having to relay and reaim the gun for every shot. The long recoil system absorbed the increased blast and pressure and allowed only the gun barrel to move backwards on the rails with the force being absorbed by the air pressure and hydrallics. The carriage remained motionless and when the gun moved back into firing position it was aimed in the exact same spot.

So, what does all of this translate into? Well, here is some raw data: 75mm caliber (roughly a 3 inch shell, weights 5.5 Kgs), max range of 6860 meters (compared to about 3000 meters for a Napoleon), a self traverse (i.e. the barrel could be moved left to right without moving the gun carriage) of about 6 degrees (not much, but remember this was the first gun that could move AT ALL), and a elevation of about 29 degrees. Most importantly (for the French) was its rate of fire: maximum theoretical rate was 30 rounds per minute, actual sustained rate (what you can shoot over a long period of time) was 15 per minute.

Pardon the pun, but this gun blew away it competition. The first truely modern artillery piece.

But here was the rub, it fit the designed need of the French military. The French wanted a rapid firing, accurate artillery piece that was mobile enough to keep up with the infantry and cavalry and could swamp the opposing enemy with firepower, usually in a direct fire (i.e. we can see them from the guns as we shoot). The French got that. But if you look at what they actually built it was a lot more that that. It could shoot accurate INDIRECT fire (shooting at something you can't see from the guns). For the first time, an army had actual artillery that could really reach out and effect the battle from a real distance. Or, if your mind had a sneaky twist, you could effect things outside the immediate battle area (the rear, units moving forward, supply dumps, road intersections, headquarters and so on). These guns added DEPTH to the battlefield and made the battlefield a whole lot bigger. And made artillery a whole lot more complex with a whole lot more problems.

Which I will hit on in the next post.

(source of technical data is "Allied Artillery Of World War One by Ian V. Hogg)


  1. Since I've read your paper I know where you're going, but this really really enlightens me with what I just read about Operation Cobra in 1944 and the Falaise pocket. It also really helps me put a lot of the historical books I've been reading that have cannon in them put them into context in that you can hit supply trains, camps, and reserves without actually having to engage them in the traditional way.

  2. Yeah. I am going to hit it with more detail as I go, but you are getting the main point. This was the death of the Commanding General being able to run the battle from horse-back. True, that notion was dying out earlier due to large sized armies, but it was the length of the battlefield that made it hard. Things were still linear, but with this type of weapon, battles now had depth. But no one was even thinking like that when this type of gun came around. The main thing for everyone was not the range and the accuracy at range, but the fact you could shoot so fast. If you didn't want your infantry and artillery drowned in fire, you had to have guns that could do the same job as the French 75. So everyone built them, and then realized that using them in direct fire was not exactly the way to go as you got your guns smashed up. That is when everyone started realizing "Whoa, wait a minute here. This weapon system is way beyond anything we have dealt with before. What exactly CAN this thing do?"

  3. Yeah, I guess before that you didn't have spotters, calls for fire, or any of that....

  4. Exactly. This gun was Ground Zero for the modern artillery revolution. Everything we do today started here. It blows my mind still that someone had to actually go "You know, how about we put the gun on the other side of the hill and have someone spot for it?"

    And be convincing enough not to get laughed at.

  5. Just had a great talk with a buddy from 428 BDE about the problems we are now discovering due to our use of "Smart" Munitions. Blows my mind. In order to use these things perfectly, we are probably going to have to completely redo every map to reflect "Eliptoid" data and height. The more things change...

  6. Oh wow - if you're having to take earth curvature into effect you really have moved into some very high tech systems.
    I was thinking why this never occurred to anyone before to have forward observers for artillery and I think it boiled down to range of the artillery up to new propellants. Before you had such far reaching range, you could always see where your round hit, so you never needed forward observers. The one exception may have been mortars lobbing shot over walls, but even then the accuracy wasn't there so FO wasn't needed until you had the range to say "wait - where did it go?".