"Some questions about abattis." Topic

Abattis was used during the Horse and Musket period as a field fortification for an obstacle formed 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 rope.

My questions are:

1. how vulnerable was abattis to artillery fire?

2. how effect were attempts to remove abattis by grappling hooks or by setting fire to the timber?

3. how effective was abattis as a barrier? Could troops force their way through abattis?

Supporting evidence for any answer would be welcomed.

TIA.

Just off the cuff.

1. It can be vulnerable. Given enough time to place a batter within range, and enough time to fire at will against it, artillery can damage abatis. I can't remember it ever having been effective on a large scale though, but I could be wrong.

2. The issue becomes whether the soldiers using the grappling hooks and trying to set fire to the barrier live long enough to accomplish the task. They have to get within close range of an earthworks teeming with enemy soldiers firing and trying to kill them.

3. The purpose of the abatis was to slow down assaulting troops and keep them in the defenders "kill zone" as long as possible, thereby killing as many attackers as possible. The more you wound and kill, the more likely the survivors will lose heart and not have the morale or drive to push the final distance to the defending earthworks. It certainly can be removed, and there are plenty of instances where the attacker got through the abatis. However, how many casualties did they incur while delayed doing so?

"The purpose of the abatis was to slow down assaulting troops and keep them in the defenders "kill zone" as long as possible, thereby killing as many attackers as possible. The more you wound and kill, the more likely the survivors will lose heart and not have the morale or drive to push the final distance to the defending earthworks. It certainly can be removed, and there are plenty of instances where the attacker got through the abatis. However, how many casualties did they incur while delayed doing so?"

Take out the word abatis and substitute the words barbed wire. Same purpose.
I have seen barbed wire in the Korean DMZ where it was placed around American positions during the Korean War. Sometimes the stuff was 20 yards across and looked like blackberry brambles. Surely that slowed down to a crawl a Chinese human wave attack!

One off the top of my head the 42nd at Ticonderoga…..over 60% casualties in a 55 yard kill zone, with none reaching the french lines.

Usual technique with abatis was to have advance squads with axes cut a path while the assault column waited under fire. I'm sure it was nerve-wracking and very dangerous.

I imagine it also depended on how good the abatis was.

1. how vulnerable was abattis to artillery fire?

Depends how thick it was but I have never heard of it being cleared this way. I doubt round shot would have much effect and period shells were not explosive enough.

2. how effect were attempts to remove abattis by grappling hooks or by setting fire to the timber?

I've never heard of it being done I suspect primarily because those attempting it would have been shot down in short order.It was generally laid out pretty close to the defenders lines so I should think trying it would be suicide.

how effective was abattis as a barrier? Could troops force their way through abattis?

It could be very effective if the material and time was available. The NVA got so good at laying it in the Overland Campaign that on at least one occasion an entire assault was called off after recon, as the Union troops recognised from bitter experience that the attack was pointless.

On other occasions abattis was forced, although not always completely. Generally it so disrupted an attack as to make the force lose momentum and cause them to be in the fire zone for much longer, taking heavy casualties and losing cohesion.

Forcing a way thorough often led to isolated groups or individuals trying to breach the earthworks beyond without success or the attack failing when supports could not arrive in time.

I get the impression that it was best used on a down slope as this gave clear field of fire to the defenders and if piled high the attackers had to fight gravity in both moving up hill and in lifting the felled trees to clear a path.

I would imagine that it was very effective in slowing an attack if the defenders had time to properly prepare it.

Even a simple downed tree is a pretty serious obstacle if you need to climb through it at the wrong angle.

Not to difficult to clear out of the way, unless somebody on he other side is shooting at you.

To protect abatis from artillery fire, and possibly to hide it from the view of attackers, early engineering books suggest that it be built in a shallow ditch. It is also recommended that the branches be pegged down to make removal more difficult.

How good was it…. all depends on two items.

1. Time to cut, drag, place, trim and position in place. A lot of manhours assuming the woods/tress are in place or very short distance away. This is not a modern logging operation with landing, skyline, communication and diesel engines….but the old fashion cut tree by axe and drag with horses.

Small positions like a redoubt or narrow passage no problem… but a mile of earthwork and abattis takes a whole lot of lumber, trees, tools and manpower/horsepower plus time.

2. Tools. Most armies carried their equipment for this work behind the main columns. So unless the army is in position for days, the start of any project like this must have strategic reasons. Armies tended to avoid encamping too long in the same position unless beforehand arrangements had been made for housing, food and sanitary issues.

Field artillery fire against abattis would be like firing at a open split rail wooden fence. You may hit the rail, or miss entirely for no effect except maybe against the earthwork/troops behind. You need to hit the main branches of the felled trees/abattis to move or clear the material. Till modern explosive shells, RS at abattis could be viewed as firing at a woods…. Never seen any game reflect "damage" to the woods themselves…just the troops positioned within. For siege level artillery or large shells/mortars, they, by their explosive capability, may clear faster.

Burn abattis? Do green trees burn well? I doubt it. With a fire starter like oil, pitch etc maybe, but you need volunteers to run under fire to toss the flaming material then wait for the fires to die down.

I view a difference of barbed wire and abattis. Barbed wire you can have trained troop lay their bodies to assist other to cross or use planks to flatten the wire. Abattis like modern positions can stop most tanks with their heavy logs till shelled apart… barbed wire doesn't stop tanks. Abattis doesn't flatten out. A musket carrying soldier can jump on top…but now he and abattis are a greater blocking obsacale.

Look at the WSS period for example of armies vs. abattis. Several WSS battles featured defenses of fallen trees (abattis). Vauban wrote a chapter on how to place, design and create effective abattis positions and made note to think about placing them in blind (hidden) positions. Continues into the GNW, WAS, SYW and even some of the early french revolution actions along the Rhine frontier.
But once the grand campaigns of Napoleon started, the movement of armies stopped the general use of abattis in large lines, except during stationary sieges.

To clear the position with axes during the assault….Ask your self how many soldiers came equipped with heavy axes….. 4-10 maybe per regiment. Too few to have a direct impact on a regimental level assault in the time permitted. The highlanders at Ticonderoga found that out during their assault. As for grappling hooks or similar, never seen in a standard army set of tools. I guess you could have a blacksmith make up a few….but what general is going to think of that problem/solution before he orders the assault…(naval captain maybe).

Finding a path though the abattis, individuals yes, platoons playing "follow the leader" yes, but companies, battalions or large formations etc…a large disordered mob creating targets. They have to cross, reform, then assault, all the time under firepower. Better hope that plan B works as plan A is just "pinning the defenders in place".

WR

For a modern cinematic treatment of abattis see the most recent film "Alamo." Apparently it was easier to scale the wall than to get to the Tennesseans' palisade.

The NVA got so good at laying it in the Overland Campaign …

I didn't know the North Vietnamese Army took part in the Overland Campaign!

Vo Nguyen E. Lee?

I didn't know the North Vietnamese Army took part in the Overland Campaign!

You know, the number of times I have to stop myself doing that and after all these years I'm still doing it!

I think I try so hard now I end up doing it anyway! :0)

Interesting 'what if' though. Army of the Potomac v NVA, who wins? :o)

I'm not sure where I read it but the USA army still teaches it's engineers how to construct an abattis

I spent 30 years in the Royal Engineers and we were taught a range of improvised techniques, using local materials if our normal equipment was not available. Certainly improvised defences, such as abbatis, and also improvised bridging. I remember one training exercise in Canada where we cut down trees from the forest, dragged them to the river and built a bridge. I suspect Roman military engineers would have used similar techniques.

It worked in the Falklands where there was no equipment bridging available and the Royal Engineers knocked down a nearby house to strip the timber beams out and make a bridge for the Household Cavalry armoured cars to advance.

Engineer comes from the same base as "ingenious" which is what engineer officers are expected to be.

Rod

As above, abatis were an obstacle analagous to barbed wire.

An obstacle is only an obstacle if covered by fire, so trying to chop down an abatis covered by fire is prety damn dangerous.

Interestingly an abatis smakes an appearance in 'The Defence of Duffers Drift', and ends up with lots of dead Boers hanging off it. Lt Foresight didn't have any barbed wire so had to made do. 'ingenious' as above.

As for Artillery remember that even when the abatis is thick it's mostly empty air. It's going to take a LOT of cannon balls to smash it anywhere near enough.

Remember abatis were felled trees with the branches pointing towards the enemy. The trunks were behind this hedgehog of brances. Putting a grapling hook in the branches leaves most of the weight on the wrong end of the fulcrum, and the brances will break off before you can pull the tree out. Then too the branches will catch on anything. How long you can do this with the enemy pot-shotting at your is another matter. Attacking the hedgehog of branches with an axe is also very futile. I cut wood all the time. The only way to lop off the branches is from the trunk end, otherwise the blow will largely just push the branch away only to string back.

Try it some time, get a machete and try hacking your way thorugh a tree's branches taken down in a sotrm. Time yourslf to see how long it will take you to get through. Divide the minutes by 3, that's how many bullets came your way in that time.

The best way to remove abatis was to burn it.

Abatis are easily cleared if undefended. If defended by fire, they are extraordinarily difficult to clear.

Interestingly an abatis smakes an appearance in 'The Defence of Duffers Drift', and ends up with lots of dead Boers hanging off it.

Good god it's years since I've read that book, thanks for reminding me of a gem.

Great answers to the questions gentlemen.

What a brilliant forum this is. For years I have wondered about the Abbatis created outside La Haye Sainte and how it could possibly have been of any effectiveness. What was there to work with? O Schmidt's comments on how to really build one (I seriously thought you just gathered what I nowadays put out for recycling once a fortnight) and what a real military engineer can teach us, are fascinating.

The shame is the accounts of that ridge south of Brussels from the chaps in green suggest that the abbatis did not survive the first cavalry assault.

You want to see a real barrier? Stand by the Gordon monument and try to get down onto the main Brussels-Charleroi road, on foot…or hands and knees. It is the one survivor of the cutting which old Vic Hugo blamed for the entire defeat. It is far more impressive an obstacle than you'd think …in 2009 or 2011 and without anyone shooting at you!

I was a combat engineer in the 1980's. They still taught abatis then although we never built one.

The textbook application was to cut a series of trees just enough to get them to fall (with the branches facing the enemy) but not completely part them from their roots. Ideally the trees will overlap, and the branches interlock. When time and resources permit you can chain them or tie them together.

The result is a mass of interlocked fallen trees still partially held into the ground by their roots. This makes it virtually impossible to pull them free.

A lot of people confuse a chevaux de frise with an abatis. The chevaux de frise is by design portable and movable. An abatis is not portable but presents a far more serious obstacle.

I'd say the biggest disadvantage of an abatis is that they might be hard to cover with fire, since the fallen trees would obstruct line of sight and would probably stop musket bullets. A party with axes might be able to find a blind spot they could cut through with relative safety.