A scout for the Brotherhood of Steel, Jensen is apt to make tactical blunders that put both himself and his teammates in jeopardy. He firmly denies that he's a liability. In fact, he models all his actions on his favorite super hero, Captain Cosmos.
After Broken Steel is loaded, Jensen is held prisoner inside a tent in the Talon Company camp at Fort Bannister. He was sent to scout out Fort Bannister in preparation for a Brotherhood of Steel assault against Talon Company in response to Talon Company's attacks on Aqua Pura caravans, but was found and captured.
Paladin Jensen and the Brotherhood of Steel assault on Fort Bannister will not appear if the player kills Commander Jabsco prior to completing the Take it Back! quest and beginning the Broken Steel content.
After speaking with the player, Jensen will charge out to attack the Talon Company forces defending Fort Bannister, where without the player's assistance he is almost certain to be mowed down by turrets and missile launcher-wielding Talon Company mercs. Soon afterwards, a squad of several additional Brotherhood of Steel paladins (who can be found waiting for Jensen to the southwest of the main entrance hiding near some rocks) will appear and attack Fort Bannister. They are heavily armed, but also outnumbered by the Talon Company mercs, and the outcome of the battle is determined by the actions of the AI actors in the combat (and any player intervention). If Jensen lives long enough, he will make a mad dash for Commander Jabsco and will almost certainly be killed by the combined firepower of an automated turret (possibly as high level as a MK VIII), the Commander activates (unless the player gets there first).
It is possible to find the rest of Jensen's squad (composed of 2 Paladins and 1 Knight with a sniper rifle, laser rifle and Gatling laser between them) directly south of Fort Bannister's wrecked Comm tower near an outcropping of rocks, the Lone Wanderer can either agree to find Jensen, leave them be or convince them to start the attack early (if you choose to attack now, Jensen will untie himself and likely go for the nearby plasma pistol then proceed to attack the fort and most likely die if the location had not been cleared of all but the Talon Commander.)
If you clear out the fort and then free Jensen, he will simply walk around the exterior of the compound with his weapon drawn (he will not run inside). If you talk to him there will be no dialogue options, but he will respond "Now that's what I call a good day's work".