yeah, Verdun was tops. The Somme was a bloody good one too.
Aside from the use of smokeless powder and barbed wire which waited until the Japanese attacks against Russia, there was powerful evidence from the Civil War on the strength of the defense.
Between the Civil War and WWI were two wars by Germany against Austria and France. The key battle against Austria was won because of the Dreyse needle gun, which permitted German infantry to hold off Austrian attacks using muzzle loaders, though outnumbered by over 10 to 1. That ability to stop Austria allowed German concentration on the battlefield and maneuver to Austrian flanks and rear. The later battles against France pitted the Germans against the French with the Chassepot rifle, largely superior to the needle gun, but Germans were able to exploit a superiority in rapid fire light artillery. It was a time of rapid innovation, and a strength in one conflict was likely to be a weakness in the next. Von Moltke (the great) managed to find an advantage and through use of telegraph and rail, was able to communicate his will to subordinates and give them the means to implement his will.
Von Moltke the later and lesser first watered down the key right flank units, and then he lost control of them, creating the weakness exploited by the BEF before Paris.