How would an Allied promise to "supply" Romania sway that country?

Question

In wooing Romania to the "Allied" side in World War I, the "Entente" powers promised Romania not only post war territorial gains, but to "supply" the country's war needs during the war itself.

The relevant Wikipedia article reads:

The Allies were to send 300 tons of provisions on a daily basis. According to the Romanian account, most of these clauses, with the exception of those imposed on Romania, failed to be respected.

The promise itself seems implausible, given that the Allies were unable to supply Russia, except in a trivial way. The World War II Persian Gulf route, had not been built, a small road from Murmansk on the White Sea to points further south was built only during the war, and the Siberian railroad was problematic. The most obvious supply route, through the "Straits," was controlled by the Central Powers (Turkey).

So what made the Romanians believe that the Entente could supply them adequately? Was it because their needs were so far below Russia's that "trivial" for Russia would be "adequate" for them?

Germany's General von Hindenberg hinted at as much by opining:

It is certain that so relatively small a state as Rumania had never before been given a role so important, and, indeed, so decisive for the history of the world at so favorable a moment. Never before had two great Powers like Germany and Austria found themselves so much at the mercy of the military resources of a country which had scarcely one twentieth of the population of the two great states. Judging by the military situation, it was to be expected that Rumania had only to advance where she wished to decide the world war in favor of those Powers which had been hurling themselves at us in vain for years. Thus everything seemed to depend on whether Rumania was ready to make any sort of use of her momentary advantage.

Answer 1

It Didn't

For a detailed description I would suggest The Romanian Battlefront in World War I by Glenn Torrey. The sparknotes answer is the 300 tons of daily supplies was a polite fiction. The allies claimed Romania would be supplied via Russia, or later via a successful breakout at Salonika. As the Russians were woefully short of the supplies Romania would need most (ammunition, artillery, machineguns) and the troops at Salonika were going exactly nowhere, the allies knew they weren't actually going to follow through. Their main barganing chip was promising the Romanians territory after the war.

The Romanians "in the know" (King Ferdinand, his senior generals, some of the pro-war civilian government) also suspected there was essentially 0 chance of the allies actually providing 300 tons of supplies a day. However Romania had long-standing territorial interests in Austria-Hungry and that combined with the general belief among both the Romanians and the allies that any change in the balance of power between the Allies and Central Powers would end the war, caused the Romanians to go for it anyway. Basically they figured the Allies would provide SOME of the 300 tons a day, and that would be enough to let the Romanian army beat the "inferior" Austro-Hungarian troops, destabilize the entirety of the Central Powers (who were assumed to be stretched to the breaking point) and end the war before the Romanian army was exhausted. In reality both the Allies and the Romanians were deluding themselves, and the resulting campaign was, IMO, the most tragic farce of the entire war apart from the repeated idiocy perpetrated by the Italians along the Isonzo river!