A redoubt is a small area that gives protection to soldiers while under attack. The word can also be used for a figuratively safe place for anyone under attack.
It is not a verb.
A related word is redan. Also a military defense location, it differs from a redoubt in that a redan has an opening for retreat, whereas the redoubt is completely enclosed.
History
The word redoubt has been in use since the 1600s. It comes from the French word redoute. As military techniques have advanced to more mobile strategies, redoubts have become less important.
Examples
Linked to a large network of subterranean command posts and military bases around Taiwan and its outer islands – as well as the U.S. Pacific Command in Hawaii – the Hengshan Military Command Center is the ultimate redoubt for Taiwan’s president. [The Diplomat]
Fort Nassau, the first Dutch trading house built in North America, was constructed on Castle (Westerlo) Island on the Upper Hudson where Albany is. It was but a small redoubt, yet deemed the acorn from which sprouted the American Middle States. [Bethlehem Spotlight]
The seaside hotel that serves as the last redoubt of Libya’s internationally recognized government is named Dar al-Salam, or House of Peace. [LA Times]
He and other elected officials from America have been welcomed in the Protestant redoubt, leaders in those neighborhoods said, in the hope of expanding their knowledge of the conflict — an understanding largely steeped in a Catholic, Nationalist perspective. [Boston Globe]
Afterwards I visited the external encampment of what will be the Parque Nacional El Impenetrable-La Fidelidad, where dozens of researchers, entomologists and biologists of various disciplines studying the last natural redoubt of what was the Gran Chaco are lodged in shifts in tents on bunks. [Buenos Aires Herald]