All battles are covered in myths I'm afraid!!
Anyway, in war all leaders take account of realities on the ground, you're right! It's just that Churchill was so good at cutting people and sides loose, whenever it suited him. The fact that Stalin never directly meddled in Greece was because he had been bought off by Churchill and co with carte blanche control of Eastern Europe, which got us all into the mess of the cold war!
As for Gallipoli, Kitchener sent an incompetent (Hamilton) to command, with no plan, no set force, and no bloody idea. Turkey was neutral, although in the German sphere, was invaded, forced to defend herself, firmly pushing her closer to the Germans, creating another sphere of operations, all for what?
To give the Tsar the city of Constantinople and access to the Mediteranean.
If Churchill had actually thought things through, the entire debacle would not have happened, which ponders the question would the Ottoman Empire have survived a tad longer?
A tit bit of history now.
The Greeks offered a Greek Army to the Allies for the Dardanelles campaign, they wanted to March on Constantinople from Thrace(overland).
The Allies, presumably with the fulll knoweledge of Winston, rejected the offer, knowing that the Greeks wanted Constantinople for themselves. Hence, the city was not captured and the campaign was a farce.
I'm sorry about your relative and the Cossack thing, if you want tell us about it!