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Originally developed and manufactured for the United States Army by American defense contractor West Tek. The T-45d power armor was the first version of power armor to be successfully deployed in battle
In 2067, the first suit of T-45d power armor was deployed in Alaska during the start of the Anchorage Reclamation in the midst of the Sino-American War. This power armor was incredibly effective against Chinese tanks and infantry. Its ability to allow a single infantryman to carry heavy ordinance that otherwise required a team of soldiers to transport and operate became key in various localized conflicts on the Alaskan front, and it allowed American soldiers wearing the armor to destroy entire towns occupied by Chinese troops without endangering themselves. In 2076, the more advanced T-51b power armor variant was introduced into combat duty.
After the Great War, this model of power armor is still being used by factions such as the Brotherhood of Steel. While main forces of the Brotherhood in the Core Region and the Mojave Brotherhood of Steel tend to use the newer T-51b, more remote chapters, such as the Capital Wasteland Brotherhood of Steel and the Brotherhood Outcasts, have to rely on these outdated suits.
The T-45d lacks the mobility of later power armor models (such as the T-51b power armor) because of its less advanced servo design; as a result it limits the wearer's Agility. The first version of T-45d power armor deployed on the front lines against the Chinese was powered by small energy cells and it burned through them at an alarming rate.
While the T-45d armor is similar in its overall shape to the newer T-51b power armor, it is significantly less advanced than its later counterpart, and uses riveted steel plates instead of plastic composite materials in its construction. Various electronic and mechanical subsystems of the armor are exposed on the outside of its casing rather than sealed within as in the T-51b, making it far more susceptible to damage. In addition, a specialized body suit is required to be worn underneath the T-45d's armored shell in order to facilitate linking the armor's servos to the wearer's own motions and to make the armor more bearable because of its heat dissipation problems.
This suit of armor also has a handle on the higher part of the chestplate, which might have been used for such purposes as storing the armor on special armor racks, or carrying an injured or killed soldier back to friendly lines to prevent capture of either the armor or soldier by the enemy.
 T-45d power armor
T-45d suits were discovered by the Brotherhood of Steel in the ruins of the Pentagon and were extensively used by Brotherhood Knights and Paladins, along with modifications and makeshift repairs. Other variations can be found in terms of coloring and other decorations.
- For the unique versions in Fallout 3, see: Linden's Outcast power armor.
- For the unique versions in Fallout 3 The Pitt add-on, see: Ashur's power armor and tribal power armor.
- For the alternate version in Fallout: New Vegas, see: Brotherhood T-45d power armor
 MP-47/A prototype medic power armor
The MP-47/A prototype medic power armor is a U.S. Army variant of T-45d power armor. It was designed to administer medical attention to the user as necessary during combat.
The prototype medic power armor has the ability to administer Med-X, which it will do if the wearer's health drops below 33%, if a limb's health drops below 25%, or if both of these conditions are met Med-X will be dispensed every 2.5 hours. Unlike standard Med-X injections, this process carries no risk of addiction. However, it does draw from the wearer's supply of Med-X, and thus the feature is useless if the player has none.
As noted in the accompanying manual, the prototype version of the suit lacks the ability to dispense anything other than Med-X, whereas the completed version would have had a wider range of features, such as deploying stimpaks. The armor was planned as an automatic medical supply dispenser, meaning troops would not have to be evacuated for medical treatment. The user manual found with the armor details that the final version was to also include a lethal chemical that would trigger if the soldier deserted.
 Behind the scenes
- The history of the T-45d was mentioned in the Fallout Bible timeline, while its designation was first mentioned in the Van Buren tech demo by Corporal Armstrong who wears the armor. The armor itself is ubiquitous in the Capital Wasteland, and the Museum of Technology has a log of proposed exhibits for 2078, which includes a suit of T-45d power armor.
- According to the The Art of Fallout 3 book, the power armor was designed directly in 3D, skipping the concept art phase.
Brotherhood of Steel Soldier in front of the Capitol Building
Fallout 3 power armor.
The power armor in the Fallout 3 teaser.
Brotherhood Paladin with a laser rifle.
A dead paladin in power armor in the Paradise Falls concept art.
Ashur's power armor/Tribal power armor