"Turn victory conditions to 1 and difficulty to Hard and work your way through all 11 maps. Can be a little bit luck based as sometimes your AI teammates will be killed (basically, whichever team gets the first kill wins), but if you squad spawn then two of you will be able to over-power an enemy bot easily enough."
All credits to SAZorlance for posting this here:http://www.trueachievements.com/a397...m?showguides=1
I haven't tried it myself yet but it should work.
hope it helps