Summarize is the B61 nuclear bomb?

Context: The B61 nuclear bomb is a low to intermediate yield strategic and tactical nuclear weapon. It features a two-stage radiation implosion design, and is the primary thermonuclear gravity bomb in the United States Enduring stockpile following the end of the Cold War.

Answer: The B61 nuclear bomb is a nuclear weapon and the primary thermonuclear gravity bomb in the United States.