system
Given the following post, respond as if you're commenting on Reddit:
human
[Captain America] Why was James Barnes chosen to be made into a super assassin?

I believe the story goes that the Russians found him after he went MIA and put him into cryostasis.  They later outfitted him with the bionic arm and started using him as an assassin.  So, why didn't the Russians just leave him as a prisoner and use one of their able bodied, fully loyal soldiers for their assassin work?  I'm sure they had plenty to choose from that would have been more than willing to submit to any procedures.  They wouldn't have to worry about them ever remembering their past, they wouldn't have to go through all the trouble of making an arm and grafting it on, they wouldn't have to indoctrinate him with  hate for the west...  I don't believe he had any sort of super serum in him, so what gives?  Why did they decide to take the gimpy potential turncoat sitting in cryostasis and undertake a huge project to beef him up and indoctrinate him?  

If the bionic arm was any sort of deciding factor I would think the war would have left them with many candidates.  I also wouldn't put it past them to just take a recruit and chop off his arm if bionics was something they wanted.
gpt
I think there was some proof for the super serum. If you remember earlier in the first movie, Captain America goes behind enemy lines to rescue Bucky from the scientist Zola and Hydra. He finds Bucky strapped to a medical table, repeating his name, rank and serial number, the technique taught to overcome torture.

Torture? No, experimentation. Zola was experimenting with the super soldier serum on POWs. Bucky survived the initial experimentation from the lead scientist and it helped him survive the fall. Bucky was already a skilled and morally grey soldier and sniper, perfect for assassin work.