Re: Klingon-Federation War of 2372-3
In the "Yesterday's Enterprise" alternate timeline, the Klingons were kicking Starfleet's ass. That would suggest the Klingons are capable of defeating the UFP militarily.
Not necessarily. Different timeline means different sequence of events. We have no way of knowing if other key players in the normal timeline were present in the darker future we saw. Even a small change could have far-reaching consequences.
"He clapped his captain—his friend—on the shoulder. Yes, this man was very much like James Kirk, in all the ways that mattered." --Christopher L. Bennett-- Star Trek: Mere Anarachy, The Darkness Drops Again