I know that Japanese invaded China in 1894-1945.
Who invaded China in 1949 to 1976? Why a child stomach could not be fed in 1970s (No war at all in 1970s) ?
Then why I could be fed in 1980's after the death of Mao? Not very much war too except with Vietnams
You may note that no big wars for China since 1945. It has been rougly peaceful.
Which Wall Mao established? In this world, which Wall will be NEVER fall?
Any Wall will fall, soon or later. Jus a common sense.