The word 防御 is formed by combining two characters, 防 and 御, which each contribute a related but distinct aspect of meaning to create a single, more comprehensive concept. 防 (fáng) primarily conveys the idea of "guarding against" or "preventing", often with a sense of erecting a barrier or taking precaution. 御 (yù) adds the dimension of "resisting" or "warding off" an active attack or invasion. Together, they form a logical and intuitive sequence: first, you establish a defense or precaution (防), and then you use it to actively resist or repel (御) a threat, resulting in the complete idea of "defense".