In the Classical Era these dudes were the nailsest of the nailsest. The Greek city states fielded the Hoplite (named for the huge shield he carried - the Hoplon). Hoplites were deployed in an eight-deep formation and in a tight block. The shields were interlocked with each Hoplite getting protection from the bloke to his right. As a result the entire formation drifted as each squaddie tried to get protection from his mates shield as well as his own - effectively they marched into battle diagonally!
The Theban elite of the Hoplites were 150 pairs of homosexual lovers grouped together into a 'Sacred Band'. Undefeated for about 33 years, they were defeated at the Battle of Chaeronea, the decisive battle in which Philip II of Macedon and his son Alexander the Great ended the independence of the Greek city states.
The weapon of choice was a 9 foot spear as well as a short shord (which had a habit of bending due to the soft bronze used in its contruction - another defence procurement cock-up!
The scariest of the Greeks were the Spartans who were the equivalent of a city populated with 1 PARA with all the problems with that you can imagine.
The Greeks somewhat disappear from history once Rome becomes dominant and they really aren't heard of for quite a while. During this missing period they are a core part of the Byzantine Empire (although they thought of themselves as Roman) and part of the Ottoman Turk Empire.
Between 1821 to 1829 the Greek War of Independence from the Turks kicked off. 64,000 Turks were in the Peloponese (Greece) at the time making up 16% of population. Half killed in first weeks of war beginning the real hatred between these two peoples.
After nabbing territory off the Turks, Albanians and assorted Slavs for most of the 19th and early 20th C (and failing to grab Asia Minor from the Turks in what became the first modern ethnic cleansing- the 'Catastrophe'), the Greeks won the first Allied victory of WW2, kicking the invading Italians back into Albania.