USA's Duane Solomon and Kenya's Boaz Lalang compete in the men's 800m heats in Doha (© Getty Images)
US champion Nick Symmonds was the major casualty of the opening round after committing a lane violation in the opening heat.
The 2009 World outdoor finalist crossed the line second behind Ismail Ahmed Ismail of Sudan, but Symmonds will be kicking himself for making such a fundamental racing error.
Ismail, meanwhile, the Olympic silver medallist, will be considerably more satisfied after running a controlled 1:46.69 to advance to tomorrow's semi-finals with the fastest qualification time.
Following Symmonds' disqualification Andrew Osagie of Great Britain was upgraded to the second automatic qualification position after registering a personal best of 1:47.70.
Isamil's Sudanese team-mate and defending champion Abubaker Kaki looked similarly comfortable in heat two, easing through as race winner in 1:47.48.
Kaki, who became the youngest ever gold medal winner at a World Indoor Championships in Valencia two years ago, remains on target to become the first man since Kenyan great Paul Ereng (1989 and 1991) to land successive titles in this event.
Behind the 20-year-old Sudanese athlete, Spain's European Junior 1500m champion David Bustos also looked in fine fettle, qualifying second in 1:47.65.
What the third heat lacked in pure quality, it made up for in sheer drama as French indoor champion Kevin Hautcoeur was rewarded for a brave front running display to claim a narrow win in 1:50.61.
The unheralded Hautcoeur led for for much of the race and repelled a late charge from Czech record holder Jakub Holusa (1:50.64) to both advance to tomorrow's semi-finals.
Kenya's sole representative in this event, Boaz Lalang served his country with distinction by comfortably taking the fourth heat in 1:49.16.
Lalang, a 2008 Olympic semi-finalist, looked every inch an athlete with medal potential to take victory in 1:49.16 from Spanish Indoor champion Luis Alberto Marco 1:49.57. Long time leader Duane Solomon of the US was swallowed up on the final lap finishing third in 1:49.69, but was rewarded by squeezing through into the semi-finals as one of the two fastest losers.
In the fifth and final heat Poland's rising star Adam Kszczot took victory in 1:50.15. with an impressive burst of speed. The World No.3 proved too strong for his heat rivals, although Austria's Andreas Rapatz (1:50.35) will have been delighted to qualify second.
Yet the final word of the round should go to Haiti's Moise Joseph, who finished a brave third in heat five in 1:50.43 but failed to advance.
"It is difficult to focus on running when you know there are many people suffering and dying in Haiti," said Joseph of the devastating earthquake which struck his homeland in January. "I am going home next week for the first time after the earthquake on a relief mission to help my compatriots."
Steve Landells for the IAAF
