Final answer:
The term for the area between opposing front lines is no-man's-land, which during trench warfare, is rife with danger including barbed wire and machine gun nests that inhibited troop movements, leading to stalemates as seen on the Western Front in World War I.
Step-by-step explanation:
The area between the opposing sides' front lines in warfare is known as no-man's-land. This land becomes a critical aspect of combat during trench warfare, as seen in World War I. The presence of defensive trenches, barbed wire, and machine-gun nests transform it into a deadly space that is difficult to cross without suffering heavy casualties. Maneuvering around the side of an army to gain a tactical advantage is called flanking. Flanking attacks were a common strategy to bypass strong frontal defenses and strike at more vulnerable sides. During World War I, the Western Front saw extensive trench systems, and attempts to outflank the enemy led to a stalemate notably exemplified by The Race to the Sea, culminating in nearly five hundred miles of frontline trenches.