Crossbones

"There are no prisoners with HYDRA, only order. And order only comes from pain. Are you ready for yours?" "Man, shut the hell up!"

- Brock Rumlow and Sam Wilson

Brock Rumlow was a HYDRA sleeper agent inside S.H.I.E.L.D. and the S.T.R.I.K.E. team leader. He is a world-class hand-to-hand fighter with an extensive experience in street-fighting and various martial arts and military combat techniques.

Early Life
Brock Rumlow was an agent of S.H.I.E.L.D. who, over time, was tasked with leading S.T.R.I.K.E.. As the leader of S.T.R.I.K.E. team, he was often partnered with Captain America and the Black Widow after the former joined S.H.I.E.L.D. During his career, he became a double agent for HYDRA, a paramilitary terrorist organization with the goal to create the fascist New World Order.

Zodiac
One operation saw Rumlow assisting in the recovery of the stolen Zodiac weapon and the apprehension of the terrorists that stole it.

During one of their missions together, Rumlow, partnered with Rogers and Romanoff, was able to stop a terrorist group led by a man only known as Baker from launching an attack with the stolen Zodiac weapon in Chicago.

Rogers and Rumlow defeated most of the terrorists while Romanoff took care of Baker himself. She wasn't able to defeat him, but realizing that, after his men had fallen, he couldn't defeat the three of them, Baker tried to flee by throwing himself out of a window.

As, Captain America was unwilling to let Baker escape with the Zodiac, he too jumped off the Skydeck and struggled with Baker in mid-air. Unwilling to die in the fall, Baker released the Zodiac to Rogers and activated his 'chute, while Rumlow snared Captain America in mid-air back on the Skydeck with a grappler arrow.

The Lemurian Star
"S.T.R.I.K.E., you heard the Cap! Gear up!"

- Brock Rumlow

Agent Rumlow led S.T.R.I.K.E., Captain America, and Black Widow on a mission to recapture the Lemurian Star, a S.H.I.E.L.D. ship hijacked by Georges Batroc and his pirates.

S.H.I.E.L.D. Civil War
After Alexander Pierce declared Rogers an enemy of S.H.I.E.L.D., Rumlow led the manhunt and captured Rogers, Natasha Romanoff and Sam Wilson on the streets of Washington, D.C.. When Jack Rollins wanted to shoot Rogers in the back of head, Rumlow noticed the news helicopter watching overhead and ordered him to wait. He then took them to a secure location to kill them but they escaped with help from Maria Hill.

After HYDRA was revealed, Agent Rumlow fought his way into the control center, and threatened to kill the man in control of the Helicarrier launch sequence. A gunfight between S.H.I.E.L.D. and HYDRA agents ensued, but Rumlow was able to get them in the air.

After his battle with Falcon, he managed to survive being burned and crushed under Helicarrier rubble when it crashed into the Triskelion.

Personality and Traits
Rumlow was shown to be incredibly loyal to HYDRA, as well as being slightly cocky, as when he saved Captain America aboard the Lemurian Star. He had a strong attitude, as well as a tendency to go to extreme lengths to do things, as when he threatened the Helicarrier controller.

Abilities

 * Master Martial Artist: Rumlow is a formidable hand-to-hand combatant. He was able to hold his own against Rogers for the longest when the whole S.T.R.I.K.E team tried to capture him in one of the elevators in the Triskelion.
 * Expert Marksman: Rumlow is a very accurate marksman and skilled in sharpshooting, being able to hit a target while parachuting.

Relationships

 * HYDRA - Allies
 * Alexander Pierce † - Leader
 * Jasper Sitwell †
 * Jack Rollins - S.T.R.I.K.E. Subordinate and Ally
 * S.H.I.E.L.D. - Enemies
 * Nick Fury - Former S.H.I.E.L.D. Director
 * Maria Hill - Former S.H.I.E.L.D. Deputy Director
 * Sharon Carter - Former S.H.I.E.L.D. Colleague
 * Captain America - Former S.H.I.E.L.D. Colleague turned Enemy
 * Black Widow - Former S.H.I.E.L.D. Colleague turned Enemy
 * Baker - Enemy
 * Georges Batroc - Enemy
 * Falcon - Enemy

Trivia

 * In the comics, Brock Rumlow is an agent of the Red Skull known as Crossbones.