Lessons from history: False statement in a book

At sixteen years, Alexander the Great was the world's leading general.

-- Buckminster Fuller, "Grunch of Giants"

This is not true.

If it is, then this is not:

Alexander was just 16 when Philip went off to battle and left his son in charge of Macedonia. In 338 B.C., Alexander saw the opportunity to prove his military worth and led a cavalry against the Sacred Band of Thebes—a supposedly unbeatable, select army made up entirely of male lovers—during the Battle of Chaeronea.

‒ https://www.history.com/topics/ancient-history/alexander-the-great

In 338 B.C., Alexander was 18. His first victory in battle is dated to 334 B.C ^[1]. He was then 24. So the first statement - that Alexander was the world's leading general at 16, cannot be true.