From the military side, Vietnam was a win. So that statement is true of Vietnam too. Politically is where Vietnam was lost. On the battlefield, air superiority led to the USA not losing one battle in Vietnam on the ground.
Part of air superiority is also defeating the air defense systems. Air superiority means you have freedom to move aircraft anywhere. An air defense systems means you cannot move aircraft in that area. So if an enemy still has active air defense systems, you do not have air superiority.
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Germany and Japan did not have superior air forces in World War II. Maybe overall they had more aircraft at the beginning, but they were unable to mass it in order to dominate the skies. Japan was spread out too thin over too large of an area. Germany gambled their air force on the Battle of Britain and lost. Through most of the war, Germany was being bombed almost at will.
Having the dominate air force is more then just have the most or best planes and its more then just dogfighting. Japan and Germany's use of their aircraft meant they were not superior.
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Michal C...
Part of the reason for Russia losing in Afghanistan was because they failed to achieve total air superiority by failing to destroy all of the air defense. If your air power cannot take out the air defense, you do not have air superiority.