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Abatis: improvised anti vehicle obstacle

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  • Abatis: improvised anti vehicle obstacle

    http://en.wikipedia.org/wiki/Abatis

    The wikipedia article gives a basic descrption:
    Originally posted by wikipedia
    Abatis, abattis, or abbattis is a term in field fortification for an obstacle formed (in the modern era) of the branches of trees laid in a row, with the sharpened tops directed outwards, towards the enemy. The trees are usually interlaced or tied with wire. Abatis are used alone or in combination with wire entanglements and other obstacles....

    ...Though rarely used by modern conventional military units, abatises are still officially maintained in United States Army and Marine Corps training. Current training instructs engineers or other constructors of such obstacles to fell trees, leaving a 1 or 2 yard stump, in such a manner as the trees fall interlocked pointing at a 45-degree angle towards the direction of approach of the enemy. Furthermore, it is recommended that the trees remain connected to the stumps and the length of roadway covered be at least 80 yards.
    I've made these obstacles in training using explosives to take the trees down. It's tricky to get the charges just right and not end up with a bunch of toothpicks. There is no reason that the same thing couldn't be done with chainsaws.

    We were taught to leave the stumps attached to the trunks, tie the felled trees together and set up booby traps to slow the clearing teams up as much as possible.

    If done correctly, an abatis can stop a tank and prevent any foot traffic on the road. A sniper team can cover the obstacle from a considerable distance and tie up an armored column for days until the enemy can bring in dismounts and engineers.

  • #2
    Re: Abatis: improvised anti vehicle obstacle

    It works better with chainsaws.

    That was something we learned from the Germans in WW2. My grandfather encountered exactly that sort of thing during the invasion of Germany.

    He described it in his book but not by name, just that there was a forest road that the Germans had blocked by felling trees in a crisscross pattern that was taking a long time to clear out. The obstacle had been spotted from the air so the advancing force knew they had to bring work parties to clear it out. They were making a day of clearing the obstacle and then discovered they had made no net progress, it looked just as big and deep as before.

    A couple of Americans from the recon unit went in through the woods, which was apparently particularly thick and nobody could get vehicles through. They encountered a group of Germans who were working two man hand lumberman hand saws and chainsaws to drop more trees exactly on the opposite side of the obstacle as the Americans progressed clearing it on the advancing side. The clearing party had been making so much noise and been so paranoid about entering the thick woods from the safety of the convoy guards that nobody thought to check and see if someone was still putting the obstacle up from the other end. They were not even sure if the Germans knew that the allies were trying to dismantle the obstacle from the other end.

    A couple of the recon element people shot at the German work party, who in turn packed up their tools and left.
    Life, Liberty and the pursuit of those who threaten them.

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    • #3
      Re: Abatis: improvised anti vehicle obstacle

      Chainsaws may work better, but det cord and C4 is so much more fun!

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      • #4
        Re: Abatis: improvised anti vehicle obstacle

        Speaking from experience, you CAN do the work without chain saws or det cord.When I was in mech infantry and the cav, the pioneer kit often came into play- axws, saws and woodsman's pal type machetes as well as regular entrenching tools.
        Gregory Peter DuPont

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        • #5
          Re: Abatis: improvised anti vehicle obstacle

          Originally posted by ISC View Post
          Chainsaws may work better, but det cord and C4 is so much more fun!
          I'll be honest, my unit trained in that a few years ago and had a hell of a time getting the trees to fall in the right direction. I mean it turned into a fiasco. Nobody would listen to me for one thing and I actually studied the stuff a lot, but we ended up having to re-blow a tree several times to the point it was easily a half case of C4 and a full roll of det cord for just the one test tree.

          All of the original demo formulas for the Abatis in my Engineer manual were done with TNT, which has a much slower velocity than C4. Most formulas had this translation thing for taking the TNT value and translating it to C4, but they simplified the formulas too much when the manual was rewritten in the 1990s and I saw the stupidest **** in the 2003 manual.

          The C4 was simply shattering a section of the trunk so quickly that it would barely displace itself, and just spear into the ground again. After the first one, the Lt would not let anyone climb the tree to put a kicker charge up high to bend the tree over so someone got the idea of putting it lower. So all it did was shatter the trunk in two places, spearing the main trunk onto the ground again, blowing foilage all over and then after the third or fourth blow, the tree went down in the wrong direction and became a widowmaker.

          If you use chainsaws, you have far far more control over which direction the tree will be coming down. I am looking at two brand/models of cordless chainsaw right now to add to my tool collection, and am leaning toward the Ryobi 40 volt lithium Ion tool system. The saw is not super big or strong, but ought to be able to quietly bring trees down which are big enough to stop non-tracked vehicles. A small crew taking turns on big chainsaws can operate just about as quickly as someone spending time to rig the demo for an abatis and then blowing it all at once, but skill and prep time to get it all to lay down like that picture is far easier drawn than done.

          Oregon Saw makes a 40 volt cordless chainsaw which goes around $400 to $500 per copy and has good reviews, but takes a $200 battery. Reports are that a guy can work all day on two batteries. The Ryobi model will be running under $200 for the saw with one battery. They already have two other tools recently on the market from the 40 volt tool system and it is no-slouch stuff. A lawnmower, a full size hedge trimmer and a full size weedeater. The weedeater might be a non-issue for tactical survival, but the hedge trimmer for clearing fields of fire is useful enough to throw in the truck, just not the ruck, and the chainsaw gets downright useful in the field when you are someplace where you don't have to hear a bunch of crap from the unit's self designated EPA representative.

          Realistically, we were looking at some stuff that the Serbs had been doing in the Balkans, with just a big tree dropped accross a road here or there, and big cables scavenged from construction cranes rigged up just right at an angle that can actually deflect a truck right down off the side of a cliff if it is anchored right on an outside curve.
          Life, Liberty and the pursuit of those who threaten them.

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          • #6
            Re: Abatis: improvised anti vehicle obstacle

            FGripper, that sounds like a terrible amount of work for anything stout enough to stop tracked vehicles, but I imagine a pretty effective obstacle against light trucks could be made from 3-4 inch trees as long as they were wired together.

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            • #7
              Re: Abatis: improvised anti vehicle obstacle

              Just a way to " draw the eye" away from what you REALLY have waiting...... why spoil a surprise?? ;-)
              Gregory Peter DuPont

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              • #8
                Re: Abatis: improvised anti vehicle obstacle

                I USED explosive to bring down lots of trees when they would get tied up with each other after storms or when I wanted to control the fall.

                The trick was to cut a notch on the side you wanted it to fall. Then pack the notch with your shaped charge. Set it off and it blows the trunk out from under the tree and the top comes down on the same side as the notch.

                The other thing was when I had a dangerous leaner I would set two charges and blow a 6-8 foot section out at one time. Don't care how tangled it would be, it would come free.
                AT one time I did... unbelievable things for this country without question, because it was my country and right. NOW, my country, that country, no longer exists and I now I feel I am the Philip Nolan of my age.
                God carries a 1911.
                Just another day towards 20...

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