Salients, re-entrants and pockets
(重定向自Pockets of resistance)
A salient is a battlefield feature that projects into enemy territory. The salient is surrounded by the enemy on three sides, making the troops occupying the salient vulnerable. The enemy's line facing a salient is referred to as a re-entrant (an angle pointing inwards). A deep salient is vulnerable to being "pinched out" across the base, forming a pocket in which the defenders of the salient become isolated. On the other hand, a breakout from the salient's tip can threaten the defender's rear areas and leaves neighbouring sections of their line open to attack from behind.