I know of the famous Percentages Agreement between Stalin and Churchill. As is commonly known, Stalin reneged on his promise in regards to Hungary, Bulgaria and Romania which eliminated all British influence by 1950, but at the same time kept his promise on Greece and Yugoslavia.
My question is, was Stalin intending to renege his promise on Greece and Turkey as well, but was thwarted? Was there a Soviet conspiracy to start/further support communist insurgencies in these countries, or did Stalin keep his sphere of influence?
Turkey remained neutral through the Second World War, and so was not part of the Balkans discussion between Churchill and Stalin at the Fourth Moscow Conference (as discussed in my answer here). As I note in that answer:
Although minority percentages were actually set in the all cases other than Yugoslavia, it is clear that Stalin regarded these divisions as all or nothing. No overt support was provided by the USSR to the Communist guerillas during the Greek Civil War of 1946-1949 despite British support for the Greek government
At that conference, no clear meaning was attached to the percentages agreed on by Churchill and Stalin and amended by Eden and Molotov. Churchill and Stalin clearly had a different interpretation of what minority percentages meant, but to state that Stalin reneged based on that is disingenuous at best.
Stalin had no choice but to keep his promise in Greece and Yugoslavia, as he had no troops in either country. The Allies liberated Greece, and Tito liberated himself.
At Yalta he had agreed to give the West (or England) 90% influence in Greece and he might have gone back on that if he had collected even 1% of the country himself. But probably not, as Stalin's agenda was more in ensuring that he would have buffer states in East Europe and that Germany would be kept down. On the north flank he wasn't hugely interested in grabbing Finland, as long as the country wasn't a platform for some kind of threat back.
In the case of Turkey, the Soviet Union had long objected to the Montreux Convention of 1936 which gave Turkey sole control over shipping between the Bosphorus strait, an essential waterway for Russian exports.
When the 1925 Soviet-Turkish Treaty of Friendship and Neutrality expired in 1945, the Soviet side chose not to renew the treaty.
The Soviet foreign minister Vyacheslav Molotov told the Turks that Georgian and Armenian claims to Turkish-controlled territory would have to be resolved before the conclusion of a new treaty1. Following the death of Stalin in 1953, the Soviet government renounced its territorial claims on Turkey.
As for Greece, American and British politicians were concerned about events in Greece and Turkey. From 1946 a civil war had been happening in Greece between its western-backed government and pro-communist forces. Truman gave $400 million dollars to Greece and Turkey and in return established missile bases in Turkey.