Together, 防 (to guard against) + 御 (to resist) create 防御 (fángyù), a strong and clear term for mounting a defense against a specific threat.
While 防御 (fángyù) is a practical term, it's deeply embedded in Chinese strategic thought. The most monumental example is the Great Wall of China (长城 Chángchéng), the ultimate symbol of national 防御. For millennia, Chinese strategy has revolved around securing borders and defending the heartland. In the classic text The Art of War (孙子兵法 Sūnzǐ Bīngfǎ), Sun Tzu emphasizes that being undefeatable lies in one's own hands, through strong defense. He famously states, “He who is skilled in defense hides in the most secret recesses of the earth” (善守者,藏于九地之下), highlighting that a perfect 防御 makes you invisible and invulnerable to attack. Compared to the English word “defense,” 防御 is used very similarly in military, sports, and technical contexts. However, when an English speaker says someone is being “defensive” emotionally, they usually mean the person is overly sensitive to criticism. In Chinese, you would more likely use a word like `敏感 (mǐngǎn)` (sensitive) rather than 防御. 防御 retains a more tactical and less personal-emotional flavor.
防御 (fángyù) is a common and important word in many modern fields.