HYDRA’s clandestine program to turn people into obedient super soldiers in the Marvel universe involved a number of gruesome techniques.
Now, thanks to the new in-universe book, The Wakanda Files, written by T’Challa’s sister Shuri, we know more about how the sinister organization transformed Bucky Barnes into the Winter Soldier. Thus far, we’ve learned about how Arnim Zola brainwashed Cap’s best friend, and why the mercenary was able to get back his past memories in the first place.
As we saw in Captain America: Civil War, all it takes to revert Bucky back to a mindless killer are coded words that have been programmed into his brain. And as the Wakandan scientist surmises, the only way to break free of the mind control is another specific trigger.
The Winter Soldier experienced this with Steve Rogers due to their powerful bond. But apparently, what they did to him has left a permanent mark. As Shuri explains in one of her logs:
“I know that some scientists can be mad. But this an entirely other level of lunacy. It’s such a fragile thing to play God with the human brain.”
It seems that the methods were effective in making Barnes “hyperaware and highly suggestible,” but it came at a cost.
“An EEG on Barnes revealed just how murky and extensive his brain damage was,” the Wakandan princess further notes. “Hydra’s Winter Soldier program subjected Barnes to electroconvulsive therapy followed by suggestive keywords and phrases to activate a brain soup knot that could take years to unravel.”
Shuri also reveals that his brain was periodically “rebooted” and that his limbic system looks like a “Christmas tree on psychotropic drugs.” Now that Cap is gone, then, this might be ill news for the Marvel superhero’s future ventures, like The Falcon and the Winter Soldier, which will ironically feature Baron Zemo as well, who knows the word sequence to reboot Bucky’s brain.