Defensive structures are buildings or constructions designed to protect people, property, and resources from potential threats. These can include walls, fortifications, and bunkers that serve as barriers against attacks or natural disasters. Historically, castles and city walls were built to defend against invaders, while modern defensive structures might include military bases and surveillance systems. In addition to physical barriers, defensive structures can also involve strategic planning and technology. For example, security fences and alarm systems are used to safeguard homes and businesses. Overall, these structures play a crucial role in ensuring safety and security in various environments.