Nuclear weapon (Earth-5875)

A nuclear weapon is an explosive device origin that derives its destructive force from nuclear reactions, either fission or from a combination of fission and fusion reactions. Both bomb types release large quantities of energy from relatively small amounts of matter.

History
The first nuclear weapon was developed by the Manhattan Project in 1942 with a scientific team led by J. Robert Oppenheimer and consisting of some of the greatest scientific minds of the 20th century, such as Albert Einstein. Subsequently, the bombs Little Boy, and Fat Man were deployed on the cities of Hiroshima and Nagasaki, on Japan, as a part of the final moments of World War II, leading to more than two-hundred thousand deaths in total.

By the 22nd century and the rise of the Interplanetary War, the first space-borne nuclear weapons were developed, but were not considered a viable weapon to use in space warfare for the next three hundred years, until the outbreak of the Secession in 2494. As the toll and cataclysm proved to be incredibly dangerous, the UNSC resorted to using their nuclear weapons in low numbers in the hopes of destroying insurgent movements.

The jiralhanae also used nuclear weapons during their societal development, leading to a global holocaust at the end of the First Immolation that sent the species back hundreds of years.

With the start of the First Contact War and the desperation of the UNSC, the organization used numerous nuclear weapons against Covenant warships, which forced the UNSC to develop increasingly more effective payloads. Because the usage of nuclear weapons in space engagements was very constant, the nuclear stockpiles of the UNSC Navy reached near depletion, forcing them to either use obsolete nukes and unorthodox tactics.

The Covenant, for the most part, did not use nuclear weapons, as they regarded them as unclean for being human weapons, with the exception of the jiralhanae. After the end of the First Contact War, however, many of the splinter groups that were born with the Covenant's downfall started to adopt more liberal policies in regards to human weaponry for the sake of surviving and thriving. Many of these factions, mostly consisting of zealots and terrorists, have acquired human nuclear weapons to kill human civilians.

FENRIS nuclear warhead
The FENRIS is an aged low-yield thermonuclear explosive. While they were originally slated to be decomissioned during the Insurrection, the outbreak of the First Contact War saw the UNSC at their most desperate for any resources and weapons, including the FENRIS.

M441 Hornet Remote Explosive System
The M441 Hornet is a 30 megaton nuclear mine deployed exclusively in space. They are designed specifically for stealth operations and are carried aboard prowlers. While they can be detected upon exiting slipspace like all other nuclear weapons, they can cool to near-absolute zero temperatures to stay "invisible".

HAVOK tactical nuclear weapon
The HAVOK is a series of 30 megaton thermonuclear bombs found in multiple distinct configurations. Arguably the most common nuclear weapon used by the UNSC, they were deployed during engagements of the Secession and later, the First Contact War.

M4093 Hyperion nuclear delivery system
The Hyperion is a nuclear missile class featured on a number of warships of the UNSC Navy, such as Charon-class light frigates. It can destroy a CRS-class light cruiser with one strike, in the case its energy shields are down.

Shiva-class nuclear missile
Shiva missiles are standard nuclear ordnance used aboard spacecraft, most commonly the GA-TL1 Longsword.

NOVA bomb
The NOVA bomb is the most powerful and destructive weapon ever created by humanity. Developed by Vice Admiral Michael Stanforth, it consists of nine warheads, which are encased within a lithium triteride shell. Once it is detonated, the NOVA boosts a yield "a hundred-fold". It is powerful enough to cause a nuclear devastation on an entire planet, and can also vaporize orbiting moons and spaceships with it.

Trivia

 * Nuclear weapon on Wikipedia.