There is no doubt that Turkey's neutrality was of benefit to the Allies, but benefit through inaction doesn't necessarily constitute alliance and may just represent fence sitting and trying to keep out of the way of the big boys. Turkey had much to loose if it got entangled in the war - Germany on one front. Russia on another and the Western Allies to their south left them vulnerable whichever side they chose and their military strength was hardly formidable. Their geographic position made them both desirable as an Ally to either side but vulnerable at the same time. Dialogue with the Allied leaders and their late declaration of war seems more realpolitik than alliance to me, but we can agree to disagree.