Quick question.....do you need a certain level of Martial Arts skills to perform takedowns? I tried starting a new game last night and gave my character the background of a Soldier. Now as I recall, he had level 2 Martial Arts, but whenever I tried sneaking up behind someone....I never got the option to do a takedown, yet in the Graybox at the start before you go out on the Saudi mission....I was performing takedowns left and right.

 

Any ideas?

Are you wearing heavy armor? If your armor is too noisy the guards will hear you and you can't take them down.