Why did the war get bogged down in the trenches?

Answer 1

I assume that it was because fire power had developed hugely in terms of accuracy and volume since (say) 1815 whereas methods of moving men under fire had not. Any soldier without protection was highly likely to be hit; the protection available at the time was limited to some well built-up fortifications (eg at Verdun) and defences that could be constructed by soldiers in the field, ie holes excavated in the ground or trenches.

In a trench men could be reasonably comfortable and fight very effectively, provided that they were not required to go anywhere. They could be relieved from the front line by communication trenches (ie also protected from enemy fire) and they could carry out a certain amount of admin (eg washing, cleaning weapons, feeding) from trenches or dug-outs constructed in the trench line. A trench (ie a line) also mean that adjacent units could protect one another's flanks.

In contrast not in a trench men were vulnerable to mines, wire, shells, and machine gun fire. Since any attack necessarily meant leaving the trench system the attackers were at an overwhelming disadvantage compared with those defending their trench. Further, even if (by assembling a vast enough body of men and support) a trench could be overcome and captured those retreating would inevitably settle down further back in a new trench for all of the same reasons. Hence any successful attack, often at great cost, would inevitably mean simply that the lines of battle were re-drawn a few hundred yards from where they had been before the attack. After attacking and capturing a trench, itself a major and exhausting feat, it was inevitable that the attacking side would need to establish their position in order to take stock, be reinforced, tend to the wounded, rest the fighting men. So the most that could realistically be achieved in a single day would be to cross no man's land (say 300 yards) and occupy the enemy's line. The displaced side would then mount a counter attack which would also have to be fought off. If that was successful (which was highly likely since, amongst other factors, the enemy's trench would not be designed to face that direction) the parties would be back where they started but with terrible casualties.

If somehow the attackers captured the enemy trench and advanced well beyond it they would be in an even worse position of defending new ground (ie digging in completely new trenches) and being much further from their rear support bases. That would inevitably make holding on to the position harder, so that there would be a tendency to revert back to the prior position. But even in those circumstances the ground gained would be minuscule distances as compared with either the length of the front or the total distance between Paris and Berlin. Meanwhile the displaced side would be establishing a new position, new trenches etc and harrassing the attackers in their new position.

This cycle, ie with limited gains from any individual attack, was inevitable so long as the side being attacked had sufficient resources and discipline to establish a new defensive position whenever they lost a trench to an attack. For the reasons set out above the new defensive position would never be that far back from the last: no one could mount an attack and then immediately advance (by foot) any great distance. In addition the attack would cost the attacking side far more in resources than it cost the defending side, because of the cost in men and morale of advancing across open country under fire as compared with firing from a concealed position in a trench. Therefore repeated successful attacks were highly unlikely.

The armies would not have got so bogged down had it been possible to outflank one another, or had it been possible to advance to the enemy (a) with protection (eg with tanks) and (b) so quickly that it was not possible for the retreating side to re-establish itself after an attack in a new position so close to the day's engagement.

Obviously if the trench line had not extended from one side of Europe to the other it would have been far less significant as the armies would have repeatedly attempted to work round each other's end. So the fact that both sides' armies were so vast that they were able to line up against one another is also relevant.