Castle defense means protecting a castle from enemies, but there are several synonyms for castle defense, such as fortress defense, citadel defense, bastion defense, stronghold defense, rampart defense, and keep defense. These synonyms connote the same idea of fortifying a structure against an adversary's attack. Castle defense has been a common practice throughout history, with different regions and civilizations constructing their own castles and fortifications. Today, castle defense has evolved into organized efforts to protect against cyber-attacks and other modern threats. Nonetheless, the same principles of strength, durability, and tactical planning still apply in ensuring the safety of the structure, the people within, and defending them against any aggressor.