Why was the Western Front so static in World War I?

Question

Once the German advance was halted, neither side could seriously advance for two years. This seems like an extraordinarily long time. Why didn't anyone succeed at going around the trenches or striking through?

Answer 1

1. There were trenches from the sea to Switzerland. There was no way to outflank them.
2. Tanks (as well as cars) were invented not long before the war, and were impractical until 1916. Without tanks, there was no way to break through clear ground protected by entrenched machine gunners.

Answer 2

As Shmuel Brill points out, there really wasn't a way around the trenches, the only choice was through, and that was a tough proposition. We're talking about ground troops who do not have significant body armor other than a helmet, armed primarily with bolt action rifles and bayonets, advancing on foot over significant distances of open ground against heavily fortified installations. While they advance they are supremely vulnerable to artillery fire and machinegun fire. They are also vulnerable to sniper and rifle fire from any of the defending soldiers, who have the ability to pick their shots. If they survive that then they have to deal with the barbed wire and other obstacles protecting the enemy trenches. And if they survive that then the real battle begins in the trenches. A battle where the attackers are yet again at a disadvantage.

At each step the attackers are at extreme disadvantage, and at each step the attackers will have their numbers cut down until any remnant forces that manage to make it to the defending trenches are so numerically disadvantaged that they are easily defeated.

Now, once those conditions begin to dominate then there are second order effects. You are not going to attack willy nilly overly much because it'll just result in slaughter, so you wait for the right time. You wait until your artillery has pounded the enemy positions a great deal. You wait until, perhaps, you have sufficient reinforcements to give your side the benefit of numbers. You wait until whatever disease has been cutting down your troops has passed and you are back to a level of strength where it's reasonable to attack. So there's a lot more waiting as well. But even so, the waiting doesn't help because the odds are so heavily stacked against offensive actions that you'd need an overwhelming advantage to break through the enemy lines. Acquiring enough ground troops for such an advantage would simply have the effect of diluting the defenses elsewhere.

It's only once technological advances and new tactics are developed that it became possible to break that stalemate. However, once broken the remainder of the war proceeded rather rapidly.