The long and short of WW1 was a bunch of inbred cousin monarchs were bickering about territories during the height of colonialism, and factioned up. One thought another country killed one of their Dukes, they denied it, were attacked anyhow, and then a barfight turned into a brawl, with the peons of each country being run into grinding machines (automatic machine guns were brand new and at the time old school block and line formations were still the normal way to group up and fight. So yeah, hundreds killed in seconds). After a few hundred thousand were dead from all over the world, the inbred officers realized war strategy had to change, and no one really knew wtf to do for awhile. More died, disease spread and killed even more, and eventually almost all blame fell to Germany (which was new and formed from various countries), and Germany got kinda punished unfairly, resulting in WW2 as Germans felt like they were punished so unfairly everyone else should pay. Very short version. Also Israel was formed at this time based on a whole shitload of reasons, that can be summed up with the British being narcissistic and doing whatever they thought was best while ignoring the political/religious minefield of their actions.