On the western front the major military strategy that led to four long years of war was

Trench warfare in World War I meant that the armies dug into trenches to hold their ground.  But it proved impossible for them to make any advances against each other.   If they would try to mount an attack, venturing into "no man's land" between the trenches, they'd get mowed down by machine gun fire.   In addition to bullets and artillery fire, trench warfare also came to involve the use of chemical weapons like mustard gas.  Trench warfare in World War I was miserable and gruesome.  

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)

the pogroms became known as kristallnacht, the "night of shattered glass," for the shattered glass from the store windows that littered the streets. the morning after the pogroms 30,000 german jewish men were arrested for the "crime" of being jewish and sent to concentration camps, where hundreds of them perished.