Grecian politics had long been divided and the new king of Greece replaced his military leaders with people more loyal to him than those who drove the Ottoman nationalists to the edge of defeat.  The new leaders lost the greatest battle of the war due to that inexperience and the Greeks fell back to lick their wounds.  They appealed for help from the other Allies, but none were willing to engage in another great war.  And then the Ottomans counter attacked.