The war started in August 1914 with the German invasion of France through neutral Belgium. When their initial offensive stall, repeated counter offensives by both sides rapidly evolved into the "race for the sea." This produced the trench line that ran from Switzerland to the North Sea.
I am convinced that most historians, who say that tactics did not keep up with technology have it wrong. The problem was that the technology of battlefield mobility and communication did not keep up with the technology of firepower. The advent of mass produced steel, high explosives, and smokeless powder (directly related to high explosives) provided greater range, greater rate of fire, and greater impact on the target to all weapons. Consequently, the battlefield was several orders of magnitude more lethal at the end of the 19th century than it was at the beginning. However, while railroads to move men and material to the front were plentiful, the primary mode of transportation on the frontline was the feet of soldiers or draft animals. Also, communication was limited to runners or field telephones. Without much better field mobility and communication the tactics employed later, during WW II, were simply not possible.
The only thing that could be applied was frontal assault.
But the modernization of the battle space in WW II amplified the ability of all sides to kill each other. More than twice as many combatants died in WW II than in WW I. It did change war in another way. From Greco - Roman warfare through the Great War the brunt of war fell onto combatants. It was soldiers, sailors, marines, and (later) airmen who killed each other. In WW II industrialization allowed both sides to target their opponent's civilians directly, and they did so. So, in WW II more than twice as many non-combatants died than combatants.
The best diplomat I know is a fully charged phaser bank.