The First World War is probably my favorite to study because of the clash of ideology and conventional war practices versus the realities of modern warfare - I like to think of it as a war with one leg in the nineteenth century and the other leg in the twentieth. Generals, especially the English, upheld this false supremacy of the cavalry charge, meaning with horses, over other, more modern means of warfare and, as a result, men were senselessly lost through antiquated techniques. It's for a similar reason, but not the only, that both the Triple Entente and the Central Powers dug themselves into trenches - it's like they were attempting a phalanx of charging men against one of machine guns.
Interestingly, the most effective war technology utilized in the First World War was barbed wire. It was very easy to construct between the trenches at night, and very difficult for the enemy to destroy. Artillery bombardments barely harmed them, as the English learned after a number of post-bombardment no-man's-land-charges. The only means to penetrate them for most of the war was with wire cutters, but it was a futile mission when the dozens of barbed wired lines defended under a hail of machine gun fire was considered. The tank alleviated this during the end of the war, but Germany's loss was inevitable by 1917 anyhow, thanks to the British Naval Embargo.
The important thing to remember, in terms of who started it, is that it was Germany's war. Nearly all parties wanted in, but Germany was the instigator who pushed Austria into invading Serbia (4 weeks after the Arch Duke's assassination, mind you), and Kaiser Wilhelm called the war one which he "planned and initiated" on multiple occasions throughout the conflict.
If you get a chance, check out To End All Wars: A Story o Loyalty and Rebellion, 1914-1918 by Adam Hochschild. It's well-constructed narrative covering the war and the social issues it provoked in Britain.