Kiwi Shane Reed was first out of the water after the 1500 metres swim but by the time the athletes had made it through the transition to the start of the bike leg, Frenchman Frederic Belaubre and Brownlee had gone to the front.
The pair were reeled back in quickly and by the end of the first lap, the lead group contained 45 athletes, including Brownlee and Clarke, as the attacks continued throughout the 40 kilometres on the bike.
Belgian Peter Croes was among those to try his luck, while Matt Reed, of the United States, sat at the front, covering the attempted breakaways. Eventually, however, Mexican Francisco Serrano and Belgium's Axel Zeebroek broke away from the rest of the lead group midway through the fourth lap.
Luxembourg's Dirk Bockel leapt across the gap to join the duo by the end of the lap and between the three riders they started to open up a gap on the main group.
Their advantage stood at 44 seconds as the athletes entered the last lap of the bicycle leg and by the end of the final climb, the lead group was down to two after Serrano struggled to keep pace up the hill.
Bockel was first out of the transition onto the 10 kilometre run, leading Zeebroek by several seconds while holding a 52-second advantage over the main field.
Brownlee led the charge after the leading pair and after 2.5 kms the main pack trailed by just 19 seconds and by midway through the lap the lead duo had been swallowed up.
Just before the end of the second lap, Spain's Ivan Rana made his move, taking Spain's Javier Gomez and Brownlee with him, while Docherty responded, as did Whitfield and Frodeno, to form a six-man group to fight it out for the medals.
The unrelenting pace eventually took its toll on Brownlee, who dropped out of the lead group - as did Rana - leaving it to Gomez, Whitfield, Docherty and Frodeno to sprint for the finish.
