Melvin Loh said:
How would the Gallipoli campaign have progressed had Gen Liman von Sanders, the head of Germany's Turkish military mission during 1915, had been lost at sea had there been a successful British submarine attack on the cruiser GOEBEN while he was aboard ?
As far as I know, von Sanders never boarded Goeben, and if he ever did, it would have been safely in port. Do you mean Admiral Souchon?
In any case, von Sanders was not all that important to the war effort. The Germans' most important contribution was filling the shortfall of staff officers and technical specialists. There were plenty of capable Ottoman commanders available, or even other Germans, like von der Goltz.
If you meant Souchon, the loss of Goeben would be serious, as it would free the Russians to act with virtual impunity in the Black Sea, and would also allow the Entente to use ships guarding against her in the Aegean elsewhere.