This was always near impossible back in the day if you were in the UK, however I started this a few nights ago (April 2010) and have now unlocked it. War Machine, on Warzone, 5 rounds, 3 minute timeout - people will jump in.
I unlocked this in the same game were the entire opposing team eventually disconnected, so "complete" probably just means don't go quiting, as host you need to see it out.