I believe actually towards the end of the war, armed with heavy siege guns, the combatants were able to destroyed huge swaths of enemy trenches.
That's why the German defenses were deep. The first line was less and less man, the main line of battle was the second line, a few km behind, while a third line protected the reserve (for the counter-attack) and artillery. Bringing adequate firepower to attack the second and third line was one of the main reason to build tank.
This is level 3 or 4 trench. The French never really did as well as the German in this area : they always packed to many people in the first line (it change only with Petain and only very slowly : as late as july 18 half the French troops were caught to far forward).
In june 16, the allies launch their heaviest barage (several day long) of the war, but it was not nearly enough (especially in the British area). In april 17, on the Chemins des Dames, the French used a far stronger barage than for the Sommes : it was even less successfull because in the meantimes the trench had become much stronger.
With air recon. enemy troops trying to counterattack were also literally torn apart.
Yep, but that wasn't from heavy artillery and are certainly not represented by barage when no one attack !
Note that air recon had little to do with it : most of the time it was pre-planned fire (because you knew a counter-attack would follow an attack) or fire asked by the infantry. Calling heavy artillery fire directly from the air in a moving situation is something that almost never happen before 40 (you need good and reliable radio, training and good organisation).
In fact, towards the end of the war the Germans felt that the offensive had overtaken the defensive because of the huge amount of attrition visited upon the defender by heavy massed artillery, but by that time they had been bled so badly, they were unable to do anything about it.
If by "toward the end of the war" you mean the offensive from mars to july 18, artillery was only one part of the equation. Even more so than before, artillery was supposed to suppress the defense (hence the use of gaz, even if by then they didn't kill much), and anyway it was all about very intense and short bombardment followed by wave of assaulting infantry. Not at all month long heavy bombardment to bleed the opponent.
And as far as those offensive goes, one should rememenber that the 2 that succeed the most has been laucnhed against weak point of the allied line. When it stroke strong point, (in the north and near Rheims), it wasn't nearly as successfull.
It's true that both side had learn to made successfull offensive (but still costly), but it wasn't by making a two month long barage without attacking.
Ni pour, ni contre, bien au contraire.
