Fortification: Fortification refers to the construction of defensive structures such as walls, trenches, or bunkers to strengthen a position and make it harder for attackers to breach.
Entrenchment: Entrenchment is when soldiers dig trenches or build protective barriers on the battlefield to create fortified positions that offer cover and protection.
Siege: A siege occurs when one force surrounds and isolates another force within a location, cutting off supplies and reinforcements in an attempt to force surrender.