In the event that the Axis powers lost World War II, the insidious Red Skull had constructed and hidden no less than five "Sleepers"--doomsday devices that would be activated in twenty years' time to continue the fight of the Third Reich. Three of those Sleepers were even designed to merge and explode, blasting to the Earth's core to produce a thermal reaction powerful enough to destroy the entire planet. Yet the Skull didn't expect Captain America to be on hand when the devices emerged and began their missions of destruction--and in each case, Cap was able to foil the Sleeper's attack and thus deny the Nazis their vengeance.
But while the Allies were fighting on many fronts during the closing days of the war, their scientists were also hard at work on preparing their own contingency plan involving a Sleeper, to be sonically activated in the event of an Axis victory. Unlike the Nazi project, there would be no delay in the activation of the Allies' Sleeper--but since the Allies won the war, the sonic signal to wake the Sleeper was naturally never sent. However, as we'll discover, the Sleeper would indeed be awakened, thirty-five years later--and as far as the Sleeper's programming is concerned, the war goes on.
Which is our wake-up call to tackle another
Marvel Trivia Question
What name did the Allies give their Sleeper--and who or what awakened it?
The cat's out of the bag (or in this case, out of the sub-basement) when our made-in-the-USA Sleeper makes his appearance in a 1978-79 cross-over story taking place in two of Marvel's popular titles:
Yes, Arsenal, presumably so named because he's a literal walking arsenal, armed with just about every offensive weapon the allies could squeeze into his frame, and whose bulk and headgear may remind you of the more contemporary Firepower. Arsenal comes to life as a result of the Titanium Man, who was remotely manipulating the near-mindless Unicorn into attacking Iron Man by way of a control signal. Defeated, the Unicorn is brought by Iron Man to the Avengers' lab, in order to save his life--but when he escapes and descends to the mansion's lowest sub-levels, the Titanium Man increases the amount of power to his signalling device in order to reach his pawn. And while that attempt is unsuccessful, the piercing signal reaches one other, now awakened from its decades-old slumber.
At this stage, Arsenal, receiving no incoming programming as yet (more on that angle later), assumes the worst, and deals with the Avengers as hostiles. This bruiser is full of surprises, and full of deadly armament--gas attacks, tracking capabilities, retracted guns, mega-strength, vacuum suction, a chest cannon--all of which are stunningly effective in dealing with the Avengers' various assaults.
We know nothing of Arsenal's origins at this point; the Avengers see him only as an invader in their mansion, and react accordingly. Iron Man is dealt with as well, when Arsenal attacks by freezing his armor with extreme cold--and soon after, the remaining Avengers are swiftly dropped. But Arsenal was likely never designed for an opponent like Iron Man, who has a few surprises of his own.
Iron Man's question regarding Arsenal's whereabouts would receive a shocking answer as the story moves to the '79 Avengers Annual, where we find Arsenal undergoing the final stages of repair following his battle with Iron Man. The location of his lair has yet to be revealed--but we slowly begin to learn more of his mission, as well as the one he now turns to for direction.
Clearly, Arsenal and "Mistress" regard the Avengers as a threat, mostly as a result of being woefully misinformed of the current state of the world due to Mistress's inability to assimilate the huge amount of information she finds when tapping into the airwaves that now pass much more data than existed in the 1940s. And so Arsenal is sent to gather human specimens to interrogate.
Meanwhile, the Avengers are provided with their own source of data--courtesy of the team's liaison to the N.S.C., Henry Gyrich, who's managed to locate a relevant scientist from the Defense Department whose memories, fortunately, date back to the war. And supplemented by records and footage from computer files and dusty storage areas, Dr. Singer helps the Avengers to piece together the puzzle of "Project Tomorrow," the top-secret project that created Arsenal and its A.I., "Mistress."
It's never explained why Howard Stark was against the use of Arsenal's capabilities following the war; we only know from Singer that, as the director of Project Tomorrow, Stark subsequently took Mistress and Arsenal offline indefinitely. The only lingering question is: Why would Stark bother with programming Mistress with the personality of a human female, prior to shutdown?
It's then that the Avengers learn that the location of Project Tomorrow is in a vast complex beneath the deepest levels of Avengers Mansion; i.e., Arsenal has been right under their noses all this time, which explains why he appeared in the mansion after Unicorn's escape and how he managed to escape without a trace. Matters are complicated when the team also learns that Arsenal has captured Hawkeye and the Beast (following Arsenal's orders from Mistress).
Sensing the Avengers' invasion of the complex, Mistress dispatches Arsenal to deal with those she believes are Axis powers who are now part of a world which fell to the Nazis. Arsenal, of course, is only following his programming from Mistress--and so while the Avengers attempt to defeat Arsenal, Cap advises Iron Man to head for Mistress, who is the key to ending hostilities. And since Iron Man is actually Tony Stark, what he initially encounters comes as a shock, to say the least.
Iron Man proceeds to free the two Avengers, and instructs Hawkeye to take the Beast and head for Cap--giving Iron Man the privacy to confront Mistress with the truth, on several levels.
Elsewhere, with Thor's power added to the assault, Arsenal is at last beaten. Unknown to the Avengers, however, Arsenal has fallen through the mansion's sub-basement floor to end up in a stream running beneath Manhattan, where it repairs itself as best it can before returning to rejoin Mistress. In our time, that takes four years--and his welcome wagon this time is the incredible Hulk (operating with Bruce Banner's mind) and the She-Hulk, along with a very flustered butler.
Even injured, Arsenal does pretty well against these two powerhouses--but once Banner allows himself to feel rage, it gives him the edge he needs to finish Arsenal once and for all.