If there is something to add to the solution or you have any qustion please tell me in the comments.
Thanks to dan aw loe
for adding that "if you have gotten this on the Xbox one you can just play the last mission and you will get the unlock since your progress saves across platforms"
This is a story related achievement.
in order to get it you will need to complete operation C
operation C consists of 5 mission.
the missions shouldn't be hard
If you are struggling with a mission i have have added a walhthrough of all mission in operation C with gold stars for this achievement:
*Warning the video might contain spoilers
C-1 starts 0:20
C-2 starts 3:39
C-3 starts 8:38
C-4 starts 11:18
C-5 starts 15:35
*Note if you are going for gold stars watch the full video and don't forget to choose the same loadouts and XP boost if needed (in loadouts)
*Note i am not the creator of this video, credits goes to: Brendan MaNiA on youtube.