Well, then you'd have Curtis LeMay's idea of sending a convoy to Berlin, daring the Soviets to attack it and start the big one.
If that doesn't start the Big One, I'm a monkey's uncle.
First Soviet Detonation of an Atomic Device (Device as in not a deliverable weapon) is August 1949, even with the Soviets overwhelming conventional numerical superiorty
the US has over 200 atomic weapons and with Fuchs and Gold snooping on the allied nuclear programs the Soviets would have good humint on the yield and probably number
of allied weapons. The only ways I see a war starting is if would Stalin descides to start an intercontinential, nuclear conflict, without himself possesing functional nuclear weapons
or strategic delivery systems, hardly a winning proposition or more likely some hardline Soviet officer taking the initiative to start the war for Uncle Joe upon seeing an American convoy roll past him to Berlin.