Actually, I’m changing my guess. The two rear supports in the back look like they bump up against the circumference of the trench. I’m thinking that they dig the trench to provide back support to the gun so it doesn’t move due to recoil. They dig it in a circle so they can swivel the gun to face a different direction.
In anycase, I’m sure some military dopers will come by and save us from my WAGing.
It looks to me like the ditch is about as far away from the center of the gun as the barrel is long. In other words, “Stay out of this area or you might get hit with the barrel”.
I think it’s where the rear legs go, no matter what the orientation of the gun. They dug the trench so the gun will be relatively level no matter what direction they are lobbing hellos.
For what it’s worth, there is another howitzer of the same type in those photos here. No trench is visible around the front end, but I do notice a little pile of sandbags just under the barrel. Perhaps both are ad-hoc solutions to prevent you from braining yourself in the middle of the night.
I would agree with the people who say it’s just a warning to soldiers walking about not to hit their heads on the barrel. You have a similar problem with sailboats – you can readily smack your head on the boom if you’re not used to thinking about obstructions at head level that do not continue down to the ground, where your eyes often are while you’re walking.
Ammo guy here. Absolutely correct. The spades at the end of the trail dig in to keep the howitzer in place. Most of the recoil is absorbed by the gun’s recoil mechanism.
I see it now. It’s easier to see if you realize that there seems to be a ‘walkway’ where the lone soldier is standing. You can see the rest of the ditch between the group of other soldiers.
OP is a picture of an M777 155 howitzer. Most everything is titanium for air mobility. Except for barrel, breech block, tires…
Here are two pictures of the older M198 155mm howitzer. Longer trails and use of sandbags to reinforce the circular ditch. I hope - first attempt at pictures.
My original WAG was going to be “So they have somewhere to throw a dud round that will help protect them if it explodes.” Then I actually looked at the linked picture and realized that the trench is far too shallow for that.
Therefore, I’ve changed my WAG to “Because that’s the way the scouts marked the emplacement location for the weapon. In other words, ‘Put your howitzer HERE inside the big circle at grid coordinates umptyfratz by lolligaggery.’”