The reason given for the start of WWI is usually the assassination of Arch Duke Ferdinand in Serbia in 1914. While it's true that was the catalyst, we often forget that the European nations had involved themselves in various alliances that led to the escalation of what should have been a relatively minor conflict.
I've provided a link below that will help a little but there's no way we can answer such a large question on a site of this kind.
There was much emphasis on trench warfare and disease in the trenches killed many combatants of both sides. It was during the war that the German's introduced mustard gas which they used on the Western Front. My father was gassed there and lost the site of one eye as a result. (He was also wounded by shrapnel.) Much of the fighting was done in "the Salient" in which the allied forces managed to force their way into the German lines, which was good, but which left them exposed on three sides, which was bad. To understand WWI you'll need to understand what happened in the trenches.
I've provided a link below that will help a little but there's no way we can answer such a large question on a site of this kind.
There was much emphasis on trench warfare and disease in the trenches killed many combatants of both sides. It was during the war that the German's introduced mustard gas which they used on the Western Front. My father was gassed there and lost the site of one eye as a result. (He was also wounded by shrapnel.) Much of the fighting was done in "the Salient" in which the allied forces managed to force their way into the German lines, which was good, but which left them exposed on three sides, which was bad. To understand WWI you'll need to understand what happened in the trenches.
