Stanislaw Ulam had numerous contributions to mathematics. He proved various theorems, pioneered multiple concepts. There is the Ulam conjecture, Ulam numbers, Ulam spiral, Ulam matrix, even an Ulam game (not as exciting as it sounds).
Ulam had another major contribution: he created the hydrogen bomb.
Yet, pretty much everyone thinks that the bomb's creator was Edward Teller. In his own profile, we called him "the father of the hydrogen bomb". In reality, Ulam and Teller worked on it together, and much of Ulam's work was absolutely essential.
So why does Teller get all the credit? Because he claimed it. He wanted all the accolades for himself, and, slowly but surely, Ulam's contributions have been whited out. Look at us: we think we know a lot about various Jewish scientists. We've heard of Teller, natch. Ulam? Not until we started to research this profile.
Nevertheless, the world can't forget yet another major Jewish scientist. Although, since his major contribution was the H-bomb, maybe it's OK that part is forgotten? We can just focus on the mathematics...