Moto2 rookie Marc Marquez fought off some early competition to take his fifth win of the season at Indianapolis
The reigning 125cc world champion dropped from pole to third on the opening lap, took the lead back on lap 8, then rode to a 1.889sec victory after cruising the final few laps.
Behind the disappearing Repsol Suter rider, Esteve Rabat, Pol Espargaro, Andrea Iannone, Scott Redding and Bradley Smith fought furiously over the remaining rostrum places for much of the 26 laps.
Former 125cc title contender Pol Espargaro eventually secured second by keeping his Speed Up FTR just ahead of fellow class rookie Rabat (Blusens FTR). Both were celebrating their first ever Moto2 rostrum.
Tech 3 rider Smith, who grabbed the lead into turn one, won a battle of the Brits with Redding for fourth place, while double 2011 winner Iannone (Speed Master Suter) lost pace and plummeted down the order.
Title leader Stefan Bradl began the race from just 22nd on the grid, after a weekend where his Kalex chassis seemed to be at a clear disadvantage relative to the Suters and FTRs.
But the young German got ever stronger in the race, snatching sixth place from the fading Iannone with five laps to go, then defending against Julian Simon (Aspar Suter).
Marquez, who has now won more races than any other rider this year, is 28 points behind Bradl heading into next weekend's Misano round. Race results:
1. Marquez (Suter) 26 laps
2. P. Espargaro (FTR) +1.889s
3. Rabat (FTR) +2.310s
4. Smith (Tech 3) +3.389s
5. Redding (Suter) +5.674s
6. Bradl (Kalex) +9.134s
7. Simon (Suter) +9.347s
8. Pasini (FTR) +15.100s
9. Kallio (Suter) +15.030s
10. A. Espargaro (Pons Kalex) +15.339s