A Few Good Men

Train five marines to five stars.

To get this achievement you will need to get 5 marines with high skills in combat, engineering, hacking and mechanical. The last four can be learnt by sending your marines for training courses (at the Military Outposts). Combat skills can only be improved when boarding ships.

Return Ship missions are ideal for low level combat marines, as abandoned ships offer little to no resistance for your marines. You will need a high enough combat rank to get M6 and higher to appear.