I finally got this just now, and I have a few ideas that will hopefully help.
1. Either specifically try for this in Tier 1 matches. You will be able to get progress towards this quite easily simply because there are only 7 enemies instead of 15....
2. Or do not try for this directly, but let it come naturally while you work on the other achievements or just have fun playing the game--this is what I did and was pleasantly surprised at the end of one match as my artillery knocked out an enemy artillery.
It pops in game when you get the final kill, I am not sure when it pops if you capture the flag though.
EDIT: Here's the very tail end of the game in which the achievement popped--it popped instantly if I remember correctly: