Because all three of those books where written by different people that were alive during the same time. . . (Judges was multiple people)
So everybody can have their voice heard and have a vote in the matter
There is not a actual designated number of deaths recorded, but it is easily in the billions
World War I completely changed the way wars were fought.
Trench warfare, which was the norm just a century ago was seen as an nonviable strategy.
Modern machines such as tanks and airplanes made trench warfare mostly about keeping ground and resulted in stalemates.
Also, it was the first time that modern tanks, planes and machine guns were being used for first time at such a large scale, resulting in an unprecedented level of death and carnage.
Military generals soon realized that time-honored military code of conducts were now obsolete and a completely new form of strategy was now required.
