During the first few months, both sides tried flanking each other to beat them. This in turn, led to building fortifications to prevent being attacked on the sides. This sort of maneuvers and counter-maneuvers created trench networks extending from Switzerland to the English Channel.
It's worth noting that it wasn't just one long narrow trench. There were miles of switchbacks, communication trenches, supporting trenches, reserve trenches, and artillery placements. Also, no man's land wasn't always hundreds of yards long. Some points along the trench forward posts were literally within an arms reach of each other. All of this on top of a haphazard maze of barbed wire, machine guns, gas, and mines not too many soldiers were eager to charge headlong into battle for a few yards of ground. Some French soldiers even protested against futile attacks.
