"What does the upside down V on the shields of the Spartans mean?"
That inverted "V" symbol is the Greek letter "L" [Lambda (uppercase Λ, lowercaseThank goodness for the Internet.
λ; Greek: Λάμβδα or Λάμδα, Lamtha)]. The Spartans used the red Greek capital
letter lambda (Λ) displayed on their shields as an identification as the people
of Lacedaemonia (Λακεδαιμωνία), which in historical times, was the proper name of the Spartan state as used by Thucydides in his histories. The citizen of
Lacedaemonia was called Lacedaemon (Λακεδαίμων).
"We are drowning in information but starved for knowledge." - John Naisbitt