TOS are written for lawyers and courts. For bilateral contracts like this there's no overarching law and legal authority, so they're more like a protocol of a verbal contract.
The lack of a binding authority means what you're really doing is communicating and clarifying your intentions. Knowing full well that either party could unilaterally chose to breach the terms.
One of the reasons that bilateral arms control agreements usually include a breach clause. "If you do X, we will do Y." Where Y is calculated to make X less advantageous.
The contract was to be enforced by the militaries of these belligerents, and to be interpreted and settled privately.
It may well be the case that this was never intended as a formal contract, but I am responding to the assertion that there was no way for it to be. I stand by the claim: the issue is authority/power, not the necessary legal means.