Those Who Cannot Remember Doc Savage...

Jess Nevins has a interesting overview of what he describes as a historical backlash against the
ideals of physical development that spawned Clark Savage Jr., and his varied companions of the pulps.
"Those Who Cannot Remember Doc Savage Are Condemned To Repeat Him: The 20th Century Backlash Against Posthuman Bodybuilders,"
While this provides some realworld relevance to the slow decline of Doc's capabilities over the years - especially post WWII - this paper suggested something much more sinister to me.
The question of where Savage went can also be asked about Kent Allard (Lamont Cranston - the Shadow),Richard Wentworth (the Spider), Carson Napier, or Anthony Quinn(the Black Bat).
Were they hunted down and destroyed?
Philip Jose Farmer has suggested that Savage disappeared during a expedition through the 'Gate of Hell' cave system near Quoddy Bay, but its pretty clear that the Russians got him:  Terror Wears No Shoes ends on a uncharacteristically down note:

" Doc Savage had replaced the virus charged money packets in the suitcase, and was inspecting them carefully with a magnifying glass.

He turned his head, said, "You'd better tell them to quarantine this suite and all the prisoners. Have them shut off the air conditioning so air from this place won't be circulated through the ship."

Canta,shocked by how pale his face was, asked, "Do you think any of the packets broke open?" "I don't think so. But we'll take no chances."

"You mean we have to remain in here for the rest of the voyage?"

"That's right. And then we'll have to be segregated for several weeks afterward. That won't be so bad--we'll be in the mountains somewhere, at a laboratory that we'll set up to find out what this virus is and dig up a vaccine or treatment."

"Can that be done?"

"It can be tried," he said. "Go on, tell them to keep everyone out of here, and keep the prisoners in the suite."

She frowned at him. He seemed detached, absorbed in the matter of solving the virus that lay ahead. There was no visible elation about him, and certainly no noticeable interest in her as a woman, and a very pretty one.

Canta felt an odd, helpless sort of rage.

She turned and went out and stood by the suite door, listening to the Captain of the Crosby Square tell expert lies to his curious passengers.

THE END "

Italics mine. 

'shocked by how pale his face was ' Savage pale with terror was a new development. I'm going to have to re-read this book to see if anything can be adduced to suggest that the Commie-spy-spreads-plague plot was actually a plot to catch the Man of Bronze. After all, everything else had failed over the years: poison and bullets, monsters and beautiful assassins.  

I've often wondered how Savage never encountered the eponymous villain Dr. Fu Manchu, although the strange entity answering to the name of Jonas Sown might well have been the Master himself.

Could Dr. Fu Manchu, (most certainly not his real name) been the surreiptious destroyer of the early twenty-century's crop of posthumans? Being apparently immortal, he could undertake schemes that would span decades, centuries even. Being subtle, he could have turned the concept of superhumanity or posthumanity into a laughable comic book idea of capes, tights and Krypton.

And now, behind a spiderweb of international banks, world-ruling corporations, and a global-marketplace of confusion and  incomprehensible wealth, does the Master rule?

Its easy to argue that the superheros destroyed the supervillians before they faded away, but no one can explain what happened to the singular greatest of the villains; tall, lean, with strange green eyes and commanding unknown sciences, the One known as Doctor Fu Manchu (known to be a pseudonym) or Kathulos or Dr. Nikola and possibly before that simply as the Creature, must still walk amongst us.