So it will be in the form of notes.
Also, by "Greek left", I mean the centre-left-liberal parties that dominated particular eras of Greek politics.
I'm going to start with WWI onwards and will not deal much with Greek politics prior to WW1 and the Balkan Wars.
Greek politics have largely been dominated by the right-wing during the course of the past 2 centuries.
The major challenge to right-wing parties came right before the Balkan Wars and more particularly during the Cretan Uprising.
A bit of background just to put this into context. As the country transformed, geographically and demographically so did its politics.
For during 1821-1900, Greece was constrained within the confines of the Peloponnese and Attica. This particular area in the corner of Europe had been in decline since the Byzantine Empire and during the revolution it became even more depopulated and largely barren of economic activity. The major Greek economic & cultural centers of the time were: Chios, Zante, Hydra, Odessa, Bucharest, Constantinople, Smyrne & Trebizond. It should be noted that even for those organizing the Greek Revolution, modern-day Romania was a more important target than modern-day Southern Greece. The Peloponnese was dominated by warlike people such as the Maniots, while Attica, Euboea and some islands were dominated by the equally warlike Arvanites. The first century of Greece was mired with constant civil wars between them 2, as well as anaemic growth and a lack of civic obedience. People like the Maniots and the Arvanites had risen up against the Ottomans, but they had largely done so for their own benefit.
Their primary concern was to push back the Ottomans, get the booty & go back home. The issue they had was that other Greek people, intellectuals, traders, and educators from these major centers had by that time flocked to the Peloponnese and had wrestled political power from the tribal Maniots and Arvanites. So a sort of equilibrium developed between these 3 groups, and eventually both Maniots and Arvanites agreed to allow the intellectuals to run politics. These intellectuals were largely what we would call today right-wing.
In the late 1800's Crete was getting anxious and several revolts started breaking out in the island calling it to be unified with Greece.
After several revolts and a couple of wars, the Ottomans granted autonomy to the Cretan state and that produced one of the finest political personalities of the century, Eleftherios Venizelos, the first PM of Crete.
Venizelos was a new type of intellectual, he was a centrist politician who effectively founded modern Greek liberalism.
A few years later, Crete got annexed and Venizelos now came to the forefront of Greek politics by launching a pan-Hellenic party and winning the elections to propel himself as Prime Minister of all Greece, Venizelos went from "terrorist" to "rebel-leader" to Autonomous Governor to Prime Minister of Greece to Vanquisher of the Ottomans within a relatively short period of time.
At the same time, the Balkan Wars break out and with a combination of luck and good fortune, Venizelos now finds himself running a country 3 times as large and 3 times as populous after the integration of Macedonia, Thrace and the islands.
Venizelos became so popular, both the King and the right-wing parties that preceded him started panicking. They started an anti-war campaign, proclaiming that electing them would mean the end of the war and the return of our troops back home. The year is 1920, Greece has won Smyrne & Constantinople and is chasing Kemal's units around central Anatolia to force them to sign the treaties.
Back home, Venizelos decides to hold premature elections to solidify his position, but he totally underestimates public opinion. He loses the elections and he loses his MP seat as well. The King and the right-wingers take over and seeing the successes of the Greek army in Anatolia they decide to forego their anti-war claptrap and push forward to capture Ankara.
However, they did not account for the fact that the WW1 Allies(namely Britain, France & Italy) are no longer subject to the treaties they had signed up with Venizelos and so the French and Italians abandoned their positions in Anatolia and stopped securing the rear and the supply lines of the Greeks. At this point in the year 1920, 24 years have passed since the war first started(1896) and Greece is standing both at the pinnacle of its achievement, having kicked the Turks out of Europe entirely and now fighting for Ankara itself. So they decide to push forward for a final blow even without the French and Italians covering their rear. They reach 10 miles from Ankara before they agreed to pack up and retreat due to a clear lack of supplies and food.
Kemal smells the weakness, attacks during the retreat and routs the Greek army. Greece loses Smyrne, Istanbul, Pontus, and Cappadokia.
Back home, they hang the right-wingers, kick the King out of the country(this is when Prince Philip was sent to the UK and later married the Queen), invite Venizelos back and the first major schism develops in Greek politics.
Ever since that moment, Greek politics will forever be marked with left-wingers(essentially liberals) and right-wingers, acrimony develops and each side accuses the other of national betrayal. The next 2 decades of 1930-1940 became even more difficult until fascism arrived to put a stop to national politics altogether.
During WW2, Greece had a fascist government of Ioannis Metaxas. Metaxas had been a Venizelist opponent, had studied in Germany and was a fascist, he decided however to ally himself with Britain and the Allies after Mussolini gave him his ultimatum. And within a few months, he died as well. When Metaxas died, other right-wingers from his faction took over the government but since the Germans arrived, they went to exile.
That meant that the Greek resistance movement developed outside the clutches of the Greek government and was largely a communist-run affair.
By the time the Germans retreated, the resistance movement had already liberated 95% of Greece and once the Germans evacuated Athens, it quickly moved into Athens too.
The Greek government in exile and its British allies came to Greece a week later and after they congratulated the resistance movement they requested it be disbanded. The communists argued that they should be integrated in the regular Greek armed forces but their request was rejected out of fear it would give them too much power and popularity and so the Civil War began even before WW2 had ended, of course British snipers were instrumental in creating the conditions for the civil war as well but that is another subject.
The communists lost the war and they were consequently tortured and deported, hundreds of thousands of Greek communists were forced to leave the country in 1949. The right-wingers were not just winners but now totally dominant in politics.
In the 1950's, a liberal Venizelos ally, George Papandreou launches the Center Union party and in the 60's he wins with the largest share ever recorded in Greek history surpassing 50% of the votes cast.
The King starts getting nervous and calls the PM in the Palace for a chat, he tells the PM that as per tradition, the King has a right to appoint the Defense Minister and the Intelligence Chief. The PM disagrees, he tells the King that this is merely a convention he had with the right-wing and not a constitutional right and that the elections have defined the government already. He should be able to choose his own cabinet 100%.
He decides to call his son Andreas, who is at the time a Prof. of Economics at Princeton and asks him to return to run these 2 offices(Defense Minister and Intelligence Chief), Andreas comes to Greece but the King continues to argue with him and his dad over their decisions. He goes further and starts criticizing them out in public. In the meantime, the Cyprus issue is raging with inter-communal violence and Andreas decides to step in, he sends 20k soldiers in the island of Cyprus to form the first Cypriot Army, this angers the British colonial authorities, who in turn call on the Americans(Lyndon Johnson at the time) to moderate the Greeks & they also called on the Turks who were instructed by the British Ambassador to use the Istanbul Greek minority as leverage, in 1955 the Istanbul Pogrom happens, the 400k Greeks leave the City forever and the Cyprus UN conference to decide on Cyprios Independence gets canceled. Britain has secured yet another divide-and-conquer victory.
Nevertheless, the Americans and the Brits start a campaign against the government and especially against the Greek military presence in Cyprus.
Amidst the turmoil and because some pro-Royal Ministers(the 'Apostates') tendered their resignation from government, an unheard-of, minor officer who was training with the CIA in the Greek army, seizes control and proclaims himself dictator, his first move was to remove the Greek army from Cyprus!
Anyway, his reign lasted for 7 years and when the Turks invaded Cyprus, the Greek universities organized a rebellion against his rule on the 17th of November 1973(we just had the 50-year anniversary 2 days ago). He sent the tanks to put them down and once the first tank breached the uni's gates, it marked the end for his regime as Greeks took to the streets and brought the regime down in 1974. This has been dubbed the 'Athens Polytechnic Uprising'.
Before 1974, the right-wing had been quite dominant in political life, after 1974, the conservatives themselves started to seriously liberalize society, constitutional safeguards for speech, assembly, and parties while personal and private rights were massively expanded. Churches, Schools & Universities were proclaimed constitutional 'safe-spaces' where armed & police forces were totally banned from entry.
In 1981, Andreas Papandreou formed PASOK(Panhellenic Socialist Movement) veering further left from his father's Center Union party and won the elections in a landslide. He invited the communists that had been banished and deported in 1949 back to the country and gave them all veterans honors and pensions.
Thus a political wound was proclaimed to have been healed.
It should be noted that the 2 major figures of Greek politics today, the current PM Mitsotakis(Conservatives) and the former PM Papandreou(PASOK) both come from the Center Union Party. Mitsotakis's dad was the Economy Minister of the Center Union government and the first Apostate. Papandreous dad was the Defense Minister and Intelligence Chief of the same government. Eventually, Mitsotakis founded New Democracy(Conservatives) while Papandreou founded PASOK.
PASOK as a party was destroyed in 2012 when it decided to go into a coalition government with the Conservatives to save the country from bankruptcy. But we may see it come back yet again, as Syriza is decomposing, and Syriza is effectively PASOK 2.0, now the dissolution of SYRIZA could bring PASOK back from the dead!
In any case, I wanted to give you an idea but more importantly to clarify the seminal moments:
Cretan Uprising brings new blood(literally) in Greek Politics.
The liberals become a dominant force until the King and the right-wingers won the elections amidst the Greco-Turkish War for the anti-war ticket.
Fascism dominates the 30's and 40's.
The Communists get expelled from the country in 1949.
Conservatives run amok, national consciousness certificates are instituted for inter-governmental and state appointments.
The Liberals come back again in 1964-1967.
1967-1974 Colonels take over.
1974 Conservatives return and liberalise.
1981 Pasok becomes the first socialist government, liberalisation goes into hyperdrive.
1986-2004 Greek Golden Age is ushered.
2007 financial crisis begins.
2012 PASOK collapses.
2023 Syriza collapses.
...take your common sense with you, and leave your prejudices behind...