Rea's challenge, however, would be limited to nothing more than the odd feigned look at turn one, Haga seemingly more confident on the brakes into the tight hairpin. It meant Spies was able to pounce in the same spot on lap five, moving into second, and although the Honda rider struck back with an identical move just a lap later, a mistake at turn three would reverse the positions again in Spies' favour.
With Rea's victory challenge fading as he ran wide at turn one on lap seven to fall into the clutches of those behind, it freed up Spies to begin hunting down Haga, who had moved 1.5secs clear as he capitalised on the exchanges behind him.
Nonetheless, Spies immediately signalled his intentions by undercutting Haga's lap times, chipping away at the margin until he was on the back of the 1198 by lap ten.
Once there, Spies wasted no time in stamping his authority, tucking beneath Haga down the back straight before scything his way through under brakes for the left-right Esses.
Now able to control the pace out front, Spies attempted to build on his advantage, but Haga was not to be shaken off, matching his moves corner for corner and never falling more than half a second behind.
Seemingly prompting Haga to begin pushing again, a new lap record on lap 15 was indicative of the pressure he was applying to Spies. Their tussle was made all the more enticing by the different race lines being adopted through turn one, which would prompt sharp intakes of breath from the enthralled crowd as they came remarkably close to touching.
After laps of threatening to do so, Haga eventually got a tow down the home straight three laps from the close to pull alongside Spies and dive into the lead at the hairpin. Nonetheless, Spies calmly placed his Yamaha back up the inside of Haga as he ran wide, immediately reclaiming the advantage.
It would prove to be Haga's final convincing act, with Spies turning up the pace again to put some air between them, Haga having concede on the final lap and dropping back to give his rival a flattering four second victory.
Not the first time Spies has prevailed in a straight fight with Haga following his last lap victory at Assen, this puts him in an ideal position to snatch the initiative when the second race gets underway.
Several seconds behind, the battle for third raged until the chequered flag, with Carlos Checa eventually getting the nod over team-mate Rea following an impressive route through the pack on the Ten Kate Honda.