Liman von Sanders is almost a traitor in Turkish popular imagination. This is rather odd considering the man spent considerable time and effort in fighting for the Ottoman Empire in the Dardanelles Campaign and elsewhere. During the Dardanelles, it was none other than him who (at least de jure) led the Ottoman Army. The Allied forces prepared to land on a strategic location on 25th April 1915. A younger Turkish officer decided on his own to move the 57th Infantry Regiment to a position from where they could counter-attack the Allied landing and prevent them from cutting the connection between Gallipoli and Istanbul. The counter-attack proved vital and decisive as the Allied forces’ advancement was thwarted. The commander who ordered the counter-attack was Lt. Col. Mustafa Kemal (later Atatürk). Here was the story of a German commander who failed to either anticipate the Allied landing at proper time and location, or worse, who (for some reason) turned a blind eye to him. That Liman von Sanders would have deliberately turned a blind eye to such a crucial movement does not make much sense. Being a German officer, elsewhere he could find it in his country’s interest to prolong the campaign, but a successful landing could effectively take the Ottoman capital out of the war and this would hardly serve German or Ottoman interests. Be it as it may, still, Liman von Sanders is the symbol of the old, complacent or ill-meaning German officers whose misdeeds were corrected by much Ottoman blood and by the astuteness of the likes of Mustafa Kemal. It does remain true that Mustafa Kemal took the initiative by himself to order the counter-attack; von Sanders confirms this much in his memoirs (p. 112). But this surely does not mean the German was deliberately detrimental to the Ottoman war effort as he (like any other commander at any time, even today) was not omniscient. Granted, the Ottoman officers at the time most likely did not hold such strongly negative feelings towards him. But, to respond to your question about his impact, it seems indubitable that he also had some negative impact on a personal level. Enver Pasha, the young minister of War, seems to have found himself at odds with the German at times. Indeed, in his memoirs, von Sanders describes occasions where Enver (who, by the way, is thought to be a relentless Germanophile in the popular imagination) actively sought to limit his authority (pp. 19-20). there was not all that much work for him to do and at times the Ottoman officers seem to have tried their best to limit his influence and impact. He did not reform the Ottoman Army per se; his role seems more to be that of presiding over it and making sure it functioned well and, presumably, in line with German interests.