What new forms of fighting styles and machinery were developed for WWI?
Unfortunately, as highlighted in the answer above, the number of casualties during World War I was unnecessarily very high due to lack of adaptation by both military and civilian leaders to the new weapons. Technological advancements gave rise to superior weapons capable of tremendous destruction but the combatants failed to alter their military strategies and tactics to suit the new developments. The popular trench warfare technique led to a stalemate between the opposing forces and alternative means were implemented to end the stalemate. Tanks were introduced on the ground as an effective means of ending the trench warfare deadlock. Airplanes that had previously been used for surveillance were introduced for dropping bombs over opponents’ territories and fighting during air battles that gave rise to the famous dogfights. During this war, artillery was improved and used to shoot down opposing enemy planes from the ground. Along with that, the machine gun was also improved to fire approximately 600 bullets per minute. Chemical warfare was also introduced and it had devastating effects. There were three types of gases that were used; tear gas, poisonous gas and the blistering agent. The tear gas caused temporary blindness and inflammation of the throat and nose while the poisonous gases such as chlorine and phosgene were toxic and fatal. The third one, blistering agent, or simply mustard gas, was the most feared of the chemical gases which after coming into contact with the skin, caused big painful blisters. In terms of naval warfare, submarines were introduced to aide battle enemy war ships. Germany, for example, regularly used submarines to sink enemy ships. Britain, on the other hand, developed underwater explosives to destroy enemy submarines. Generally, even though technology enhanced the weapons that were used during the First World War, the military strategies and tactics did not evolve to suit the new developments.
Sadly for the soldiers involved, there was much more new "machinery" than there was in the way of new "fighting styles." Military tactics had not kept up with military technology and the result was a blood bath.
There were a few inventions that were new to the war but had little impact on fighting styles on land. These included airplanes, submarines, and poison gas.
The most important new technology in the war was the machine gun. This invention gave defenders a huge advantage. They could dig in in their trenches, set up machine gun posts, and decimate any enemy charges coming across open ground. Officers still thought that simple head-on charges were the only way to win, but the machine gun made a mockery of that idea.
Because of the machine gun, WWI developed into a stalemate of trench warfare. Eventually, one invention helped to end this situation. This was the tank. Tanks were able to drive over barbed wire and trenches while destroying machine gun nests, allowing attackers to penetrate defensive positions. The development of the tank and of infantry tactics coordinated with tanks, helped to end the stalemate created by machine guns.