Iron Maiden’s ‘Two Minutes to Midnight' takes on Def Leppard’s ‘Photograph' in round one of Ultimate Classic Rock's March Riff Madness competition.

In a grueling process that involved more than a few hurt feelings, we've selected 32 of classic rock's most iconic riffs and paired them off in 16 first-round duels. Over the next five weeks the field will be repeatedly cut in half by your votes, until we theoretically arrive at the most awesome riff in all of rock history.

This duel pits the New Wave of British Heavy Metal’s twin champions against one another. Iron Maiden became the leaders of this crucial musical movement thanks to a string of monumental metal albums to start the ‘80s, and ‘Two Minutes to Midnight’ is just one of their many, instantly recognizable riffs.

Def Leppard, meanwhile, were quick to try and dissociate themselves from the N.W.O.B.H.M. in their bid to conquer America, but before they swapped hard rock riffs for mega-melodies, the quintet crafted an all-time-great with 1983’s radio and MTV-conquering ‘Photograph.’

So who will win this contest between reluctant peers? You can vote once per hour until round one of March Riff Madness closes on Sunday, March 9 at 11:59PM ET. The whole thing gets settled with the announcement of our big winner on Tuesday, April 7.

Watch Iron Maiden Perform 'Two Minutes to Midnight'

Watch Def Leppard Perform 'Photograph'