To get this achievement, you must have 200,000 Command Points at once. I found it was easiest to go to Missions option from the main menu, knock the difficulty up to 3 star, and play Mission 2 of Chapter 1. The reason is because its easy, with 5 enemies, and a watch tower. Plus you can work towards the Grenadier achievement also. Just kill all enemies with grenades, and collect both dog tags, and you will get 10,950 command points in a couple of minutes.
Hope this helps, and if anyone has any improvements I can make, comment, and I will edit the solution and give you credit.
Edit: According to xXSCUMMXx, they didn't play the game for a few days, and acquired free points when they loaded the game. An alternative to gaining points if you don't get to play much, or cant be bothered with a grind.
Edit 2: Shadow Kisarugi has checked and confirmed that you get a 25,000 command points bonus every 24 hours. I cannot confirm this myself, as I have uninstalled the game to make room for new games due to low storage space on my Lumia. Can anyone else confirm this?
Edit 3: Dragon Weew has informed me that yes the game still gives points out every 24 hours. But now that amount is 10,000 command points. So you can still boost it, but it will take a twice as long if that is your chosen way of boosting this achievement.
Edit 4: An update from AKXone. If anyone can confirm this, I would be grateful.
I think there has been another update as I'm only receiving 5,000 points every 24 hours and I'm no longer receiving a difficulty bonus when completing the mission more than once. Completing mission 2 on hard awards just 6,400 points now.