This background is that in the 1970s, China vigorously developed its air force and trained pilots, who demanded high eyesight. During the War to Resist US Aggression and Aid Korea in the 1950s, we were severely suppressed by the US Air Force. China has always been the main force of the army, but the air force is weak. Chairman Mao and other * * * only called on the people to "protect their eyesight for the revolution" from childhood for the sake of national defense and revolutionary forces.