I want to know the answer to the following question:
What often caused strife between Greek states?
All the background I'm provided with is that "Both Athens and Sparta were later overshadowed by Thebes and eventually Macedon, with the latter uniting the Greek world in the League of Corinth (also known as the Hellenic League or Greek League) under the guidance of Phillip II, who was elected leader of the first unified Greek state in history.". Is that enough to answer the question?
Answer: no