The answer I’ve usually read is that the mechanization of war (tanks, jeeps, etc.) made trenches ineffective. Why is this so? Can’t see why a big ole’ ditch wouldn’t be able to stop a tank from moving forward.
Sua
Trenches didn’t work in World War II for the same reason they didn’t work in World War I: The machine gun. The idea in WWI was that your troops would dig a big ditch to hide in, and the enemy would dig another big ditch opposite, for them to hide in, and then at some point one army or the other would all jump up out of their own trench, and run over to the other guy’s trench to shoot them. Only problem with this is that as soon as you jump out of your trench, the other guy’s machine guns mow you down.
Trenches were never intended to stop vehicles, and I’m not sure how one would dig a trench which could stop a tank. Sure, you could do it given enough time and heavy equipment, but it’s not something you can carve into a battlefield in the middle of nowhere on a few hours’ notice.
The mobility of tanks would also reduce the usefulness of trenches. Opposition dug in ahead? Fine. Just drive around them or drive at them with your infantry crouched behind the tanks. Get close enough and the infantry can dive in and even the odds.
If trench warfare had been tried in WWII on a large scale, I think it would certainly have hastened the use of tanks like this or this or this.
I’ve read about the creation of “tank traps.” Not just cul-de-sacs with men with AT weapons at the end, but actual pits to get tanks to fall into. Employed by the Russians against the Nazi advance in WWII, but I’m afraid I can’t recall the exact reference. Of course, the whole point of these would be to hide them. Position them at a natural bottleneck, and hope the enemy falls in. So they don’t exactly cut it as “trenches.”
I’d hazard that increased fire control and utilization of air power played a role in the decline of trench warfare. Trenches didn’t provide the best of coverage against artillary even in WWI; they had to dig damn deep bunkers and hide in those during the actually shelling. But fire control was such that you had to let up your shelling or risk slaughtering your own infantry as they attacked. So then it became a race between your guys getting across no-man’s land, and their guys getting out of their bunkers and to their guns.
Basically, however, I’d say the deciding factor is/was the mobilization of the battlefield. Without the peculiar static conflict of WWI, trenches really don’t make tactical sense.
I’d recommend John Keegan’s “The Face of Battle” (along with everything else he’s written). The conclusion especially deals with the mobilization of the modern battlefield.
-ellis
And, of course, aircraft became much more deadly. It doesn’t do much good to hide in a big ditch when a plane could just fly along and strafe you. That wasn’t quite as big a problem in WWI.
Ahhh, the Funnies !
Another item that is usually forgotten, is improved communications. Wireless radios made a major difference in warfare. When in WWI they had to rely on pre-planned artillery fire during an attack, in WWII, the artillery could be on call or you could even call an airstrike on a strongpoint. Not only that, with good communications and motorization, you could react more rapidly to unforessen events. Just look at the military records of those armies with good communications (Commonwealth, U.S., Germany) and those with poor ones (USSR, 1940 Commonwealth, Italy, Japan).
Didn’t chlorine and/or mustard gas cause a major problem with entrenched soldiers as well? Being heavier than air, it sank into the trenches & voilà! Instant corpses already in open graves, just add headstones.
A real military historian should correct me on this, but IIRC Trench Warfare originated towards the end of the US Civil War (in some of the sieges in Virginia) as a response to the reality that by then, in the face of advances in weaponry (early repeaters, more efficient single-loaders, better artillery), the time-honored tactics of marching and standing in formation in the middle of a field while shooting volleys at other guys also marching and standing in formation, and then charging with bayonets, had become a recipe for butchery. The theory became that you’d hole up in your respective trench, wait for the artillery to blast the bejeezus out of the other guys, then go “over the top” to do a shooting charge at the survivors – and when you got to his ditch, still give ‘im the ol’ bayonet.
But properly designed and dug WWI-style trenchworks are no mere “ditches” – after the artillery barrage many of the other guys are alive and able to man their guns. And since you still require a mass infantry charge to actually take the ground, you have to stop your own shelling. By 1914, the defender can then take advantage of several new technologies: slow down the charge in the middle of a free-fire zone by laying down barbed wire tangles and passive mines – which stay put during the barrage – and open up with machine-guns from hard cover. Butchery squared.
This is no way to fight a war, unless you can spare hundreds of thousands of casualties per week (which the WWI powers seemed to notice only too late…) . Trench Warfare, complete with human wave attacks and gas, was briefly revived in the 1980s by Iran and Iraq, along their southern front.
detop: I’m with you on the importance of communications making it possible to figure out your next move as-things-happen (including calling in artillery, air support, armor; or ordering an orderly retreat before a unit’s cut off or completely routed) as opposed to a predesigned set-piece plan.
Trench warfare was not “the plan” in WWI. Initially, it was believed that horse cavalry would provide sufficient mobility, as it had in all [sub]( or, almost all)[/sub] wars before it. But the modern machine gun ended all that. Small & light enough to be quickly transported to an area where cavalry was operating, it cut the horsies into horsemeat. Which made the French chefs happy, but not the generals.
So, they fell back on Infantry & artillery.
Artillery isn’t very mobile, neither is infantry. So, swift attacks were impossible. All the “punches” were “telegraphed”, when the infantry tried to move. Artillery greeted them. So the dogfaces dug in. And so did the other side. They would try to “rush” the other guys’ trenches. Artillery & machine guns would massacre them. And so forth.
Trench warfare was not planned. It evolved.
Any unplanned tactic is * always* a disaster.
That said, there was a sort of trench warfare in WWII. Japan fortified islands, dug trenches & tunnels, & garrisoned islands throughout the Pacific. This is trench warfare.
We responded to this by ignoring most of the garrisons.
The US just attacked those islands whose location made them important, or destroyed the islands’ airfields by air or naval bombardment. The others were isolated from re-supply ships, & left to starve. We sailed around them. This is called “stratgic mobility”.
Armies on islands with no way off aren’t very dangerous. 
Actually, IIRC, tank traps appeared during the Spanish Civil War and their goal is not as much as stop the tanks as to channel them towards a position where AT defenses will rip them apart.
Attrayant, contrary to common opinion, gas was not a very deadly weapon during WWI. A powerful psychological and incapacitating one, yes, but not very deadly. According to William Moore in his book Gas Attack (Leo Cooper, 1987), the British Army suffered 124,702 mustard gas casualties (mostly blisters, burns or temporary blindness) of which 2,308 died between July 1917 (when mustard gas started to be used) and November 1918. The total gas (all-type of gases) casualties for that period were 160,870. Chlorine gas was only used as an expedient during the first few gas attacks.
As my social studies teacher answered when I asked him this, “Hitler was a man in a hurry.” His blitzkreig campaigns didn’t leave time for trench warfare as he had France out of the war very quickly. The major land enemy that Hitler had to fight was Russia, and he wanted to invade them quickly to get to the oil in Asia, IIRC.
Additionally, I think that the advent of airplanes as air-to-ground weapons would make trenches very vulnerable.
Of course the aforementioned reasons also, plus, knowing what a disaster trench warfare had been in WWI, who would want another round of it?
Actually, Allied armies did use trench warfare in WWII. The French set up the largest system of fixed foritfications in the history of warfare, the Maginot Line, which extended from The Franco-German-Belgian border area all the way to the Swiss frontier. The German armies just attacked at the weakest point (Belgium), broke through, and circled around behind the Maginot Line and drove toward Paris. The advances in mechanization after WWI made static defense obsolete. In WWI, tanks were very primitive, automotive transportation was undependable, and there weren’t many paved roads. The pervasiveness of paved roads, especially superhighways, are the result of military necessity (Hitler directed that the first such system be built to ensure that his rebuilt military could get anywhere quickly. Eisenhower did the same in the US later.)
Tanks, communications, aircraft and specially trained troops were all were important in ending the strategic importance of trenches. This was discovered before the end of WW1, and hastened it’s end.
In their last offensive, during 1918, the Germans utilized highly trained shock troops and concentrated their attack on a small front. Shock troops were trained to make a breakthrough and leave isolated strongpoints to be mopped up by the regular troops. They achieved a large breakthough and given better transportation, might have delivered a decisive defeat on the Allies.
Conversely, the Allies final offensives were successful, in part at least, because they finally had large numbers of tanks at hand.
One could argue that the majority of the First World War was an attempt to finally discover a tactic (and the arsenal) to overcome the trench.
What exactly were those vehicles intended to be used for?
The first two were Armoured Vehicles Royal Engineers or AVRE. The big bundles you see in front of them are called fascines and are used to fill trenches, ditches, bomb/shell craters so as to ease the passage of vehicles.
As for the third one (on the Sherman tank cahssis), I will have to hazard a guess, either a bridge carrier or an armoured rocket launcher (the frame reminds me a little bit of the Land Mattress weapon system).
In the last couple of months toward the end of WWI the British finally learned how to co-ordinate artillery and foot soldiers using the rolling or creeping barrage.
The range of the guns was wound out as the troops made their way forward, and they ran too, using whatever cover was available, so the shells were going right over the heads of the troops and landing not far in front of them.
They also did not use an artillary barrage to soften up the enemy which usually just forewarned them and had proven disastrous and relied instead on a sudden attack using 600 tanks as the spearhead.
Add to this a more integrated approach using tanks to hit particular strong points and close air spotting support and it can be fairly said that the British more or less invented Blitzkrieg.
This assault convinced the Germans that the allied armies were capable of taking any territory they chose, epecially since a difficult and dangerous crossing of a large and well protected canal in highly defendable countryside was crossed and those protecting it were brushed aside.
In many ways it was a total war approach since it had demanded more efficient use of industrial capacity, to produce the tanks in such a short time especially.
Add to this the effects of the blocking of Germany which could not then compete with this renewed industrial capacity.
This was a very innovative campaign using all the lessons learned from the previous four years.
These lessons were not missed by the German generals who refined them further still in WWII.
As Bosda Di’Chi of Tricor has noted (and as others have mentioned), the trenches of WWI were historically an accident. The trench is a siege weapon/tactic. It allows an army to place itself fairly close to the weapons of its opponent while sheltering them from fire and allowing that army to communicate up and down the line (rather than dodging from rock to tree to get messages passed). In September, 1914, the monstrous armies of Western and Southern Europe had become locked in a struggle in which neither side could simply overwhelm the other with a massive charge or create a serious break in the line with a good cavalry offensive. In effect, each side laid siege to the other.
Trenches were used in WWII and again in Korea. They appeared wherever a siege developed (as at Anzio or among some of the Korean hills that could be held but from which an irresistible attack could not be launched).
Well as several posters have pointed out there were quite a few points of trench warfare in WWII. There are a lot that haven’t been mentioned. Basically anytime someone was being attacked or anticipated attacks they threw up fortifications and dug trenches. The Maginot line is of course the most famous but there were litterally dozens of others, although they varied widely in size and quality. Many of these were built in anticipation of the war, but a good number were built during the war. Generally the armies avoided the fortified lines whenever possible. However when they were forced to take defended lines the campaign generally slowed to a crawl even when the attacker dominated the air and overwhelming odds of men and material. The Italian campaign was a great example of this.
In addition WWI was not as dominated by trench warfare as we tend to see in the West. The Balkan and Eastern campaigns were always more fluid and trenches were never as widely used.
The third tank is described elsewhere on the linked page as:
I wasn’t aware of the Spanish origination. But I was aware of the general usage of “tank trap,” and I was trying to distinguish from that. Like I said, this was not designed to funnel the tanks to an AT position. These were actual pits. Like the classic Gary Larson “dig a pit and cover it over and hope the dinosaur falls in” cartoon. Except for tanks. And they probably lacked sharp sticks at the bottom.
-ellis