Isn't the military might of Sparta an example of history written by the losers? I mean one important source for the Peloponnesian War was Thucydides, who was on

Isn't the military might of Sparta an example of history written by the losers? I mean one important source for the Peloponnesian War was Thucydides, who was on the losing side of the war. And when writing his book, he might have wanted to cast himself in the best light possible, by depicting his victorious opponents as the best military in Greece?