Liverpool drew first blood against Manchester United with a 2-0 win at Anfield in the first leg of their Europa League last-16 clash.
It was a night of firsts as Daniel Sturridge's maiden European goal, from the penalty spot, teed up Louis van Gaal's first defeat against the Reds after four straight wins for United against their arch rivals.
Sturridge's first-half strike -- his first in continental competition in only his fifth appearance over three years -- was followed by Roberto Firmino's close-range effort 17 minutes from time.
And had it not been for the continued brilliance of goalkeeper David de Gea, it would have been over as a contest before next week's return at Old Trafford.
Manchester United manager Van Gaal had spoken of not living in the past. Liverpool counterpart Jurgen Klopp had said he did not believe in enemies in football, but an atmosphere crackling with electricity certainly did not reflect that.
Thursday night's encounter may not have had the ferocity and intensity of some of their Premier League battles -- Jordan Henderson's yellow card inside two minutes was for a high foot routinely punished in European football rather than anything more aggressive -- but there was no mistaking the importance.
Liverpool's football in the first half was played primarily in United's half as they dominated the midfield battle with a front four of Sturridge, Firmino, Adam Lallana and Philippe Coutinho rotating positions with bewildering regularity.
There was no wonder the back-tracking Memphis Depay was lured into bringing down Nathaniel Clyne in the area after the advancing full-back collected Firmino's outside-of-the-foot through-ball.
With regular penalty-taker James Milner absent with illness, Sturridge -- criticised for not taking a spot-kick in the Capital One Cup final shootout last month -- stepped up to beat De Gea for his fourth goal in six appearances against United.
The Spain international kept his side in it during the opening 45 minutes with three brilliant saves.
Coutinho's decision to go at Sturridge's far-post cross with his right foot and not his left gave the goalkeeper just enough time to get back and claw out his shot, while his save from a one-on-one with Sturridge was Peter Schmeichel-esque and the point-blank stop from Lallana's volley was just pure instinct.
Had Juan Mata gone down amid a tangle of legs with Mamadou Sakho, Spanish referee Carlos Velasco Carballo -- who has given 80 yellows and six red cards in his 13 matches -- would have been duty-bound to award a spot-kick in front of the Kop, but the former Chelsea man stayed on his feet and the danger was cleared.
Michael Carrick replaced forward Marcus Rashford, who apart from one half-chance in the opening minute had a quiet night, at half-time as United tried to gain a foothold in midfield by switching to a back three with the substitute at its heart.
It had the desired effect as United enjoyed a spell of dominance but De Gea continued to save his side, denying fierce drives from Coutinho and Clyne while Henderson saved him the trouble by wastefully firing wide.
He had no chance with Firmino's close-range stab -- his third goal in eight days -- after Lallana capitalised on Carrick's decision not to clear his lines.
Marouane Fellaini headed wide a rare chance but United rarely exposed Liverpool's aerial fallibility.
They will have to do much better next week if they are to rescue a European campaign which began with back-to-back wins in the Champions League - a competition they may not qualify for next season.