The Novichok or N-series nerve agent — used in last week’s attack against Russian ex-spy Sergei Skripal and his daughter Yulia in Salisbury, U.K. — is distinct from the better known G- and V-series nerve agents, which unfortunately have become more familiar after their use in Syria and by terrorist groups.

How it works: Nerve agents interfere with neurotransmitters, causing involuntary muscle contractions, impaired cardiac function and airway restriction, potentially culminating in death by asphyxiation. They interfere with the nervous system in stages, making rapid decontamination and treatment essential.

Novichok is up to 10 times more potent than the VX that was used to kill the half-brother of North Korean leader Kim Jong-un last year. It can penetrate NATO chemical protective gear and was specifically designed to be undetectable using NATO and U.K. sensors.

The bottom line: The use of Novichok represents a deadly game-changer for chemical warfare and nonproliferation. It demands global condemnation and an insistence that Russia account for how the nerve agent came to be used at all, much less on foreign soil.

Daniel M. Gerstein, a senior policy researcher at the RAND Corporation and adjunct professor at American University, was formerly the acting undersecretary for Science and Technology at the Department of Homeland Security.