Redoubt is often used in military situations to describe a fortified defensive structure. The general ordered the construction of a redoubt to prepare for the impending siege.
Pro Tip 2/3
Figurative Usage
Redoubt can also be used figuratively, implying a safe space where someone retreats or has a strong stance. His office was a redoubt where he felt secure from the chaos.
Pro Tip 3/3
Literal vs Metaphorical
Distinguish between a physical fortification and a metaphorical place of security or defense. The protesters used the university as a redoubt for their ideas.