If they time it right they could make the Iraq Revolt work. The Germans badly needed Turkey to be able to move supplies into Syria, but didn't have it IOTL, but here they could rail things in and use it as a staging base for expanding Middle East operations. Making the Iraqi revolt stick would be a disaster for the British and might even get Iran to be a lot more strident in their pro-Axis leanings. Getting Iraq as an ally, plus perhaps even Syria/Lebanon as an on going front would be extremely helpful to Rommel, but would require more German divisions through Turkey, which might well be a major problem for Barbarossa. However the German 2nd and 5th Panzer divisions did not take part in Barbarossa and were in fact involved in Greece/the Balkans and had their equipment lost when being shipped from their to Italy for redeployment. If they are instead tapped for Middle East operations based out of Turkey, say a Middle East Corps to complement Rommel's Afrika Korps efforts their transports won't be where the British submarines found them, so they won't lose their equipment can follow up their Greek efforts with a Middle East vacation. Two Panzer divisions in Iraq/the Middle East would be a major problem for the British, potentially a fatal one if met with an Arab revolt in Palestine and perhaps even Iran throwing in with Hitler.
Iran is in large part untouchable to the British if Iraq is in revolt/free of British troops. If the Germans play their cards right Turkey then could lead to a total unraveling of the Middle East for the British and probably the Fall of Egypt. The Jews in Palestine will be in a VERY bad position. Later Turkey would be a critical base for operations against the USSR in the Caucasus, but in 1941 if Barbarossa is going to happen it will be a very important transit point for shipping and warships. IOTL Turkey did not allow warships through the Straits, which would have been extremely helpful against the Soviet Black Seas Fleet. Having Italian submarines hunting from Romanian ports against the Soviet supply effort for Odessa and Sevastopol would have been incalculably helpful to the Axis in Barbarossa and after. WW2 would be quite different if Turkey joins and much worse for the Allies. Not sure how it would play out in the long term, too much depends on how badly the British do as a result. If their entire Middle East position falls apart and Iran is not invaded and thus doesn't open the Persian Corridor for Lend-Lease things are going to be very rough for the Allies. The Medditerranean Front would probably collapse and the North African theater would be an Axis victory by 1942. Barbarossa would be different, not necessarily worse for the Axis depending on butterflies. 1942 would be very different if the British have been defeated in North Africa, the Middle East, and Iran is pro-Axis and not allowing Lend-Lease and isn't occupied by the Allies. Rommel might well be out of North Africa and in Russia, same with the Luftwaffe that was in the Mediterranean because that theater is wrapped up. In 1942 Turkish, Iranian, and German mountain divisions could end up invading the Caucasus and without Iranian route LL the USSR would be in serious trouble there.
Lots of interesting butterflies...but why would Turkey want to do this???
I know this is a necro but at 5 minutes in this guy quotes this whole post and others from this thread verbatim. Feels like someone should tell you guys when your content is used without credit. Not just reworded or for inspiration. A direct quote.
Also turkey joining the Axis or the Soviets (because of occupied or not) really has such a massive influence on the war that I'm surprised there aren't more recent threads.
Anyone got a timeline about it more detailed than the posts in this thread? There must be a realistic way to do this with a pod around anschluss