Name: John Walker
First Appearance: Captain America #323
John Walker first started out as the Super-Patriot (Captain America #323, 327) who was a super strong showman. He hired three of his friends to attack him so he would beat them to make himself look good. Captain America was forced to resign or become a servant of the government (Captain America#332). The government picked the Super-Patriot as his replacement having heard of him. Captain America has given him his costume and shield so those were given to Walker to become the new Captain America. Walker was more of a violent Captain America during his period in this role.
Next in Captain America#341 his identity was revealed to the whole world. The effect of this was Walker's enemies the Watchdogs captured his parents. Walker attempted to save his parents but ended up dying. Walker became insane, killing seven of the Watchdogs while crippling many others.
At the time Steve Rogers no longer being Captain America became the Captain and wore a black version of his costume and carried a vibranium shield that the Black Panther donated to him. Walker eventually met up with him and they discovered that the Red Skrull has hired the plenty of the villains that Walker had gone against.
In Captain America#350 Steve Rogers had been given his uniform back and resumed the role of Captain America back. While in the next issue Walker was apparently assassinated by a Watchdog. The government wanted to kept Walker as an agent so they gave him the uniform Steve Rogers wore as the Captain and the shield that went with it renaming him the US Agent. The government then brainwashed him so he couldn't remember his past and that his parents has been killed. He joined the West Coast Avengers so that the government could keep watch on the team. Captain America didn't have a problem with this as the Avengers could keep a watch on US Agent as well.
Later the US Agent found that he has been brainwashed and sought out the ones responsible who restored his memories of his past. Eventually by Avengers West Coast #69 the government no longer wanted him and he had his freedom. No longer been forced to be on the team by the government when elections for members of the team were held he only received one vote causing him to leave the team in anger. He would later rejoin them in West Coast Avengers until the team disbanded. He took a new energy shield and costume when a new team was created called Force Works.
Us Agent had been hired by Edwin Cord to lead the Jury to capture the Thunderbolts.There first attempt failed but with Edwin Cord refitting their suits they were preparing for another attempt. Wanting to help stop Graviton when he was in San Francisco his idea clashed with Edwin Cord. US Agent was used to Tony Stark's backing of the Avengers. US Agent wasn't happy when Cord wouldn't allow him and the Jury to help because it would risk Cordco's investment in them. The last meeting between the Thunderbolts and US Agent and the Jury (Thunderbolts#32) resulted in helping the Thunderbolts against the Imperial Forces of America instead of arresting them. This went against what US Agent was hired to do but it was the right thing for him to do. Since he could deal with the authorities better than the Thunderbolts could and he could make sure all the Imperial Forces that were defeated that day could be brought into custody. Due to helping the Thunderbolts Us Agent likely no longer works with Edwin Cord or the Jury.
Thunderbolts and all associated characters are the property of MARVEL COMICS TM&©2003.