The development in weaponry that had the greatest single impact on the war was the invention of the rifled musket. The weapon of choice before the war was muskets that had no spin on them. The new rifles solved old technical problems of other muskets. They had a spiral to spin the bullets faster, straighter, farther, and with more accuracy to 500 yards. In the premodern era, they only shot 50 yards. These rifles made it possible for soldiers to shoot with greater accuracy from a greater distance. It made battlefields large scale. The modernized guns and bullets are developed and used widely from the Civil War (1861-1865). The new technology of weapons eventually inspired trench warfare.
WWI was a war of many firsts, the first time machine guns were widely used by opposing armies as well as long range artillery. Generals and military strategists of the time had no idea how to use a weapon.
The result was large human wave attacks that were launched at these new weapons the same way they would charge a cannon in previous wars. The only difference is, a cannon fires one shot and requires typically 3 men to operate and aim it. This was a very time consuming process and if one side were to charge it with enough troops, there was a good chance of taking it. In WWI they tried to use this tactic against machine gun positions with very deadly results. Thousands of man ran to their bloody death at the hands of machine gunners. A machine gun crew could expend thousands of rounds in a matter of minutes pick the weapon up and move to another position in a blink of an eye. They just could not overwhelm it when it was in a defensive position.