Themistocles was an important figure in Greek history because he encouraged Greece to create a strong navy. Encouraging his fellow Greeks to increase their naval power was something that Themistocles done multiple times throughout his career as a politician.
Why is Themistocles important to Greek history? He freed all the Greek slaves. He led the Greeks to victory at the Battle of Hemius. He led the Greek army against Xerxes. He encouraged Greece to create a strong navy.