The right answer is The land was mined territory and was subject to artillery, shelling, and gunfire.
The WWI initiated and different way of battle, it was called "industrial war". Battles were not decided by superior generalship or skillful endeavors but decided via the total annihilation of the other side. For this matter, they compacted thousands of men in rat-infested, constantly flooded, moody trenches. This kind of combat was responsible for 60% of the war casualties. The land between the two different sides was mined territory and was subject to artillery, shelling, and gunfire. After hours of the crossed fire, soldiers engaged in a suicidal attempt to invade the enemy side just to be welcomed by their well-defended machine guns.