Turkey remained neutral through most of the war
Had the Axis been able to convince Turkey, which had fought on the side of the Germans in the First World War, to join them they would have a created a land bridge from the Caucasus to the southern Russian front, as well as gaining the support of Turkish troops. Diplomatic overtures to the Turks continued for most of the war. Germany and Turkey signed a non-aggression pact in 1941, only days before the onset of Operation Barbarossa. But further efforts to have Turkey fully ally themselves with the Axis forces remained futile. Turkey remained officially neutral, positioned like a cork sealing the Germans from southern Soviet republics.
Had Turkey joined the Axis it would have had implications for other actions in the Persian Gulf region, as well as the southern flank of the Russian front. In 1943 and 1944 Germany sent over 100 locomotives and supporting rail cars to facilitate the shipment of chromite ore it wanted to purchase. The United States and the British intervened to purchase as much of the ore as they could, despite not needing it, in order to deny it to the Germans. When the Soviet Union overran Bulgaria in 1944, Turkey was cut off from the rest of Europe, and in February 1945, under Soviet pressure, Turkey declared war on Germany, entering the war three months before its end.