I personally rather not speculate too much on the Temporal Cold War for now...too little is known and since B&B aren't written ST: Nemesis, it would be rearing its ugly head in the next big screen production.
For now my personal advice is not to think too much of the Temproral Cold War unless you want to be proven completely mistaken by canon...I don't think we'll learn anything about it before the season climax of Enterprise...besides is Enterprise really part of the continuity anyway? Too many differences have emerged between Enterprise and previous canon so either we're dealing with an alternate time line or B&B have done their usual hack job...
Arise, arise, Riders of Theoden!
Fell deed awake: fire and slaughter!
Spear shall be shaken, shields be splintered,
a sword-day, a red-day, ere the sun rises!
Ride now, ride now! Ride to Gondor!
Theoden King: The Return of the King