Shackleton saved every one of the men he had left behind. Overwhelmed is more like it, which is undoubtedly why the museum created the exhibit, why Caroline Alexander curated it and wrote the book about the expedition, and why all those who see the exhibit ought to be brought to their knees. By endurance we conquer. It exists in other forms, of course, though it's not so dramatically visible. Where the goal is not reached, one only has the unrealization, the unfinishing to go on, so that what is not done becomes what is done, and that, being done, becomes victory.
Endurance is conquest.
The true feat of Shackleton's expedition was his voyage to save his men. The 800-mile journey has been called the greatest voyage ever, because of the seamanship, to be sure, but also because it arose unexpectedly, and so was a test of human reflexes and the adjustment of human intelligence. Since Shackleton put the lives of his men first, it was a display of moral intelligence. But this ocean journey showed the other stuff that people are made of. Endurance is conquest.