On the home stretch for the first time, defending champion Mal Whitfield moved forward, past the other chasers into a marking position on Ulzheimer.
Steines lost ground, getting passed by a big rush by Albert Webster, but Nielsen pressed Ulzheimer to the line, Ulzheimer taking bronze with a lean then in the next step doing a face plant to the track.
Whitfield equalled the Olympic record he had set in London four years earlier, meaning he ran exactly the same time 1:49.2 in both races.
Whitfield became the second man after Douglas Lowe to defend the 800 metres title.
[1] Cuba, Ghana, Guatemala, Israel, Pakistan, Puerto Rico, the Soviet Union, Thailand, and Venezuela appeared in the event for the first time.
Great Britain and the United States each made their 11th appearance, tied for the most among all nations.