VX7 Nerve Gas

VX7 Nerve Gas was a chemical weapon developed by the UNSC in 2494, in order to prepare to stop a full on civil war from erupting in the colonies. VX7 was based off of the deadly VX nerve agent from the 20th Century, however, UNSC chemical warfare specialists had changed the formula to make it even more deadly. The gas was used repeatedly in the Human-Covenant War to stop the mainly Unggoy horde style attacks the Covenant favored to overwhelm UNSC ground positions. During the battle of Delta Halo, Jiralhanae forces captured VX7 canisters the UNSC In Amber Clad had dropped for the UNSC forces. After the war, all stockpiles of VX7 in UNSC custody were destroyed.

Development
VX7 Nerve Gas was developed in the early years of the Insurrection as a chemical weapon in the case the Insurrection spiraled out of control, and it needed to be stopped without razing colony after colony completely to the ground, as what happened with. The compound itself was developed by Doctor Bartholomew Tiswin, who finally perfected the formula in 2500, a month after which the gas went into production.

Insurrection
During the Insurrection, VX7, in the UNSC's hands, acted merely as failsafe, never used in combat against the rebels. However, on three separate occasions from 2506-2525, terrorist cells of the Insurrection procured VX7 gas, loaded it into missiles or rockets, and threatened to fire them at civilian targets. On two of the three, the insurgents were neutralized and the gas recovered before they could do any damage, and in one instance, the rebels did fire a missile, however, due to the Insurrectionists' inexperience with the missile and its systems, the weapon missed, and landed in a nearby lake.

Human-Covenant War
When the Human-Covenant War erupted in 2525, the UNSC saw an opportunity to use the VX7 gas in combat, with the Covenant's heavy use of large amounts of cannon fodder to try to overwhelm their enemies. In multiple battles, the UNSC used the gas against the Covenant, not only in stopping hordes of the aliens, but also to stop the Covenant from getting their hands on sensitive information that the UNSC did not want to lose, firing a chemical warhead to kill the Covenant, but not destroy the data they wanted to recover.

In 2552, when the UNSC engaged the Covenant on Delta Halo, it also dropped canisters of VX7 to aid the UNSC forces on Delta Halo. However, some of the canisters were captured by the Jiralhanae, but, for an unknown reason, did not use it.

Post War
After the Human-Covenant War, as another sign of peace, the UNSC ordered all stockpiles of VX7 in their possession to be destroyed immediately, it being a remnant of a bygone age that was no longer needed. Following these orders, the UNSC used mass drivers to fire casings full of the agent into a star, allowing none to use it. Despite this, there were several instances of teams leading raids on rebel compounds finding stockpiles of the nerve agent, likely to have been left behind by the UNSC and then taken by rebel troops, but there were no reported attacks with it by 2565.

Effects
VX7 was a nerve agent, that could be absorbed through inhalation, ingestion, or skin exposure. According to Doctor Tiswin, the symptoms of VX7 were: "VX7 is a cholinesterase inhibitor. Stops the brain from sending nerve messages down the spinal cord within thirty seconds. Any epidermal exposure or inhalation and you'll know. A twinge at the small of your back as the poison seizes your nervous system. Your muscles freeze, you can't breathe, you spasm so hard you break your own back, at least that's what our hypotheses have yielded."

- Doctor Tiswin after being asked what VX7 does to a human

Delivery Systems
VX7's original main delivery system was by canister, bomb, rocket, or missile. However, when the Human-Covenant War began, the UNSC deployed a VX7 mine, designed for use to stop Covenant infantry advances dead in their tracks.

Uses
VX7's main use is as a mass killer, as it, being a gas, is able to spread far, and the lethal dosage to kill someone is extremely low. Along with this, VX7, much like its 20th Century predecessor, is also effective as an area of denial weapon, as its properties allow it to hang in the area where it was dropped for long periods of time.

Protection
The only protection from VX7 contamination is a chemical suit or power armor such as MJOLNIR, the foremr issued to UNSC forces operating near VX7, or in combat zones where VX7 is prepared for use. However, if one is contaminated by the chemical, one must immediately inject the antidote, composed of multiple medications. The antidote is issued in the form of autoinjectors to all UNSC troops.