The Rosenbergs weren't extradited from a country which would require a formal guarantee that the death penalty would not be used, so are not a relevant precedent.
I bet the formal guarantee will be negotiable, especially when on the other end is the US. That's why UK has a special relationship after all. Assange would have been safer in Russia than UK for sure.
It's not an unprecedented thing. Mexico forced the US to agree not to seek the death penalty for Joaquín Guzmán ("El Chapo") before extraditing him, and the US has kept to that agreement.
The Rosenbergs were executed for treason, not just sharing some secret documents. They actively spied for an adversary of the United States, recruited other spies, and stole some of the United States' most powerful secrets.
The gravity of what Assange and Manning did doesn't compare to what the Rosenbergs did, which is why Manning didn't get a life sentence or death penalty, and why Assange won't either. Only way Assange ends up on the precipice of capital punishment is if he did far, far worse things than what has been revealed so far.
Rosenburgs were not convicted for treason, but espionage.
The judge convicting them worked along with the prosecutor on the bar to make sure that they got a clean cut, and more easily prosecutable charge of _espionage_ instead of original treason. But yes, his ultimate reason was his personal insecurity about seeing his fellow Jewish American giving the public even more reason to doubt the loyalty of Jewish Americans (given how all things were at the time...)
Excerpt from wiki.
> Kaufman is best remembered as the judge who presided over the espionage trial of Julius and Ethel Rosenberg and imposed their controversial death sentences. Roy Cohn, one of the prosecutors in the case, claimed in his autobiography that his influence led to Kaufman's being appointed to the case, and that Kaufman had imposed the death penalty on Cohn's personal advice. This claim has not been verified, although it has been shown that after Kaufman learned that the FBI and Justice Department opposed death penalties in the case, he asked the prosecution to withhold its recommendation before issuing his death sentence. In his summing up Judge Irving Kaufman was considered by many to have been highly subjective: "Judge Kaufman tied the crimes the Rosenbergs were being accused of to their ideas and the fact that they were sympathetic to the Soviet Union. He stated that they had given the atomic bomb to the Russians, which had triggered Communist aggression in Korea resulting in over 50,000 American casualties. He added that, because of their treason, the Soviet Union was threatening America with an atomic attack and this made it necessary for the United States to spend enormous amounts of money to build underground bomb shelters." [5] Kaufman said that he had gone to synagogue to pray before issuing his death sentence; this enraged Supreme Court justice Felix Frankfurter, who later wrote to judge Learned Hand, "I despise a judge who feels God told him to impose a death sentence," and also told Hand that he was "mean enough" to stay on the court long enough to prevent Kaufman from having a chance to take Frankfurter's place in the so-called "Jewish seat" on the Court.[4][6]
You're right, the actual charges they were convicted of were espionage. Still, the point I'm making is that Assange's actions are nowhere near what the Rosenbergs did. Unless we see some superseding indictments of worse stuff.
Interesting historical perspective on how/why the death sentence was sent down, I didn't know that part about the judge.
