Bridgeheads refer to strategic positions that are established in enemy territory, enabling the attacking army to advance and gain control over a certain area. Synonyms for bridgeheads include foothold, bastion, beachhead, stronghold, and redoubt. Each of these words refers to a position of strength that is established in a potentially hostile environment. A foothold is a position that is gained in unknown territory, while a bastion is a fortified structure that provides a safe haven for military forces. A beachhead is a landing spot on enemy shores, while a stronghold is a fortified position that is difficult for enemy forces to attack. Lastly, a redoubt is a stronghold that is surrounded by additional fortifications, making it virtually impenetrable.