I am a bit skeptical that by 1912 there were already in production in the USA trucks who could reliably go cross desert (it takes a 4-wheel drive). By 1940 these trucks certainly existed but 30 years earlier? It is however sure that no army had motorized divisions at the break out of the war and it would be at least less that generous to accuse German and Ottoman not to have been " bright enough to see the obvious thing"

. In September 1914 gen. Gallieni had to send 10,000 men from the garrison of Paris to the front on the Marne river to support the VI Army. 6,000 of these reinforcements were transported to the front in 600 Parisien taxis: I'm inclined to believe that if Gallieni had a couple hundred trucks available he might have chosen to use them. This happened in France, not the most backward country in the world.
You fantasize having an army of at least 50,000 men plus all the artillery, the pontoons and the supplies being transported across 300+ km of wild desert. It would have been an unbelievable performance in WW2 (and nothing of this order of magnitude was ever tried). In 1914 it would have been impossible and more than that unthinkable. We are in some very deep ASB territory here