So what have we got so far in the way of “hard lessons learned by 1918”? I count:
The rolling barrage: lay down an advancing wave of shells with your infantry following up as fast and close as they can.
Special trench-storming tactics and weapons (including the first sub-machine guns).
Tanks- primitive, slow, and unreliable tanks, but better than nothing.
At least some attempt at better communications: spotter planes with portable wireless sets, etc.
Sorry to resurrect a fairly old thread, but I just today read about another innovation that was available by the end of the war:
(5). The trench mortar. Effective man-portable mortars were a key weapon in the “trench storming” tactics used in the 1918 German offensive.
I strongly recommend anyone interested in this have a read of Military Power by Stephen Biddle.
He makes a fairly well-supported argument that the main cause of the WW1 debacle was a failure to adapt tactics to the massively increased firepower extant on the modern battlefield, despite the British having developed most of the necessary techniques during the Boer War. When the Germans finally sorted this out on a large scale during the spring 1918 offensives, they made huge gains despite not having any significant material or technical advantage compared to earlier failed offensives.
Whether you agree with him or not, he provides a great deal of useful information.
I read an interview with a German soldier who fought in one of the first major battles that the USA took part in - I can’t remember the name, but it was some named after some wood or forest. He said something about knowing that the war was lost when the Americans won a battle using 1915 tactics in 1917, through sheer force of numbers. So even at that time it was recognized how much war had changed in the last couple of years.
Bellau Wood.
It’s certainly true that the arrival of the U.S. Army during lkate 1917 was very discouraging to German leadership; having defeated Russia, and successfully fending off the British and French while doing so, they were now suddenly faced with a fresh new army equipped with a limitless supply of men. It must have been awfully depressing, like winning a boxing match through 11 rounds and then in the 12th round, they replace the other boxer with a new guy.
The miles long, pivoting maneuver was impractical if not impossible. It’s hard enough to maintain a straight, continuous line of troops in a turn on the parade ground.
When the French army concentrated and attacked at the Marne there really wasn’t much else the Germans could do but concentrate in order to not be to badly outnumbered. This opened the gap you mentioned. A description of the opening days of the war contains this.
Given the benefit of hindsight I’d like to think the commanders would have improved their intramural communications so that mass attacks wouldn’t be neccessary. Such attacks were suicidal in the face of machine gun and artillery fire. A more spread out force has a much better chance of not being wiped out in the first 100 yards.
By the end of the war my understanding is that air attacks reasonably well coordinated with ground action had been developed, and I suspect a lot of engineering ingenuity would have been put into improved tanks.
Although WWI Generals were pretty slow learners I can’t believe they would have pursued the same methods that cost all of them a large fraction of a whole generation in casualties. Call me a cockeyed optimist.
Generals are always fighting the last war.
If they knew in 1914 what they knew in 1918, WWI would have been like WWII.
I think you are. The battle of Verdun was intended to cause as many casualties as possible. The plan was basically to “bleed white the french army”. By this time, the human cost was quite well known, but it was still part of the headquarte’r’s stategy. Losing say, 150 000 men was apparently perceived as worthwhile as long as the enemy would lose 200 000.
Depressing French cynicism. I’ll bet Maurice Chevalier wouldn’t have been so negative. 
But you are probably close to right. And it wasn’t only the French Generals. The British didn’t change methods all that much after their disasterous assault at the Somme. Although they did recognize the problem and developed tanks to try to solve it.
Actually, in this case, it was the German generals. They weren’t really trying to make a breakthrough, they intended to create a major, months-long meat grinder in the hope that it would severely weaken the french army and/or make it lost resolve. Or something. It was an attrition fight. And, apparently, they didn’t mind much losing hundreds of thousands people themselves in the process.
The German high command apparently expected twice as much casualties on the french side, for some reason (in reality, the losses have been more or less equal) The meat grinder part worked perfectly. 700 000 died for Verdun (and I assume an uncountable number were wounded) in ten months. Thinking that such a level of losses (that would be a sizeable part of either country’s whole population) to take (or keep) a town could be considered as worthwhile is just mind-blowing. Seven fucking hundred thousand people!
IIRC Lord Kitchener was one of the very few that recognised that this would be significantly a war of attrition, attrition of people but also of resources.
I als think this comment was made quite early on, perhaps before the first Christmas when the war was supposed to be finished according to the Genreals of the day.
Mind you, its all very well having accurate observations, and Kitchener was not at all popular among the Genral Staff for this comment, but its quite another thing to come up with a solution.