As tensions across the Korean peninsula continue to simmer, reports are now circulating that South Korea’s military forces are prepared to use so-called blackout bombs in any future conflict. These high-tech weapons have only been used a handful of occasions before – most notably during the last two Gulf Wars and during the conflict in Kosovo – so what exactly are they?

Classified until only recently, these weapons are decidedly non-lethal. They contain millions of small particles of chemically treated carbon filaments, essentially a type of graphite. The individual particles are smaller than 0.025 millimeters (around 0.001 inches), which means that they’re tiny enough to be breathed in but not necessarily the right size to get lodged in your lungs.

When this strange type of cluster bomb detonates, these particles are released into the air as a cloud, which then “rains” or scatters down onto the surrounding landscape.

Graphite – thanks to its odd chemical structure that allows it to contain free electrons – conducts electricity with ease. That’s why these bombs are targeted at major power grids and lines: when these particles make contact, a current flows through them at such extreme temperatures that it melts part of the mainline wiring, and the system shorts out. So long as the power lines aren’t insulated, these graphite bombs can be incredibly effective.

When they were first deployed in the 1990 Gulf War against Iraq by the US Air Force, up to 85 percent of the country’s electrical supply was knocked out. Similarly, when used by NATO forces against Serbia in 1999, 70 percent of the country’s power grid was shut down.

At the time, even after the weapon's canisters were located, no-one was sure how they worked. Pentagon spokesman Ken Bacon said back during the Kosovo War: “We have certain weapons we do not believe it is appropriate to talk about – and this is one of them.”

South Korea’s Agency for Defence Development has been working on them recently, and has, according to Yonhap News Agency, almost finalized their version of the design. It’s part of the ominous-sounding Kill Chain program, one which aims to detect an impending attack by North Korea and respond pre-emptively.

Any such first strike by the South would involve taking out as much of the North’s border artillery and rocket launching sites as possible, many of which are constantly pointing at the capital, Seoul. Blackout bombs could disrupt vital power lines that are used by the North to relay commands from the leadership to its military units.

At the very least, blackout bombs are designed to have a psychological effect. Knowing your enemy can flip the switch on a nation’s electricity supply is a powerful tool, even without it being used.