I read in Knox, MacGregor (1986).
Mussolini Unleashed 1939–1941. Politics and Strategy in Fascist Italy's Last War. Cambridge: Cambridge University Press.
ISBN 0-521-33835-2. page 233 that Turkey threatened to intervene if Bulgaria joined in against Greece, citing the Balkan Pact.
"With Bulgarian neutrality assured—following the terms of the
Balkan Pact of 1935, the Turks threatened to intervene on Greece's side if the Bulgarians attacked Greece—the Greek high command was free to throw the bulk of its army against Italian forces in Albania.
[119] "
"By 3 November, Badoglio had realized that the situation was "very delicate." It
was now clear that Bulgarian neutrality posed no threat to the Greeks; the
Turks had hinted that they would strike if King Boris moved. The Greeks
could therefore concentrate practically all of their army against Italy, and a
large portion of it against the vulnerable Italian left flank."
So let's say Boris goes for it, calling Turkey's bluff. The POD can be that the Germans force Romania to have over south Dubrovgea at the same time as Transylvania What are the results?
If anyone knows where I can find details on the Turkish diplomacy surrounding the invasion of Greece I'd love to be directed there. This is the only information I can find on what seems like a very significant decision.
We also have other mentions that suggest if Greece did well Turkey and Yugoslavia would have gotten involved:
"A decisive Greek victory
might induce Yugoslavia and Turkey to join a common front; at the very
least, it would ensure that Greece and Britain could concentrate without
distractions against the Germans when the latter attacked."
Or Germans striking at Turkey
"Worse, German buildup in
Rumania presaged a spring offensive against which Greece would be helpless. Greek collapse might lead to a further German advance through Turkey
toward the Persian Gulf and Egypt. Mussolini's prediction in one of his
periodic efforts to cheer up Graziani that the threat to Greece would distract
the British from finishing off North Africa was proving correct. "