rearguard; rear guard
Military term for the unit protecting the rear of a formation. Often contrasted with 前衛 (vanguard).
See also: 前衛
The rearguard unit held off the enemy's pursuit.
Sports term for a player positioned in the back line, such as in soccer, rugby, or basketball.
He plays as a defender on the soccer team.
前衛 refers to the leading/forward unit or player, while 後衛 refers to the rear guard or defensive position, both in military and sports contexts.
後衛 (a rear-guard or defensive position, e.g. in volleyball) shares the kanji 衛 with 護衛 but refers to a tactical position, not the act of protecting someone.
Compound of 後 (rear) and 衛 (guard, defense).