In 1991 the US Navy used a warhead it had developed for the Tomahawk cruise missile to black out power supplies over much of Iraq.
These so-called Kit-2 warheads - whose use was only revealed a year later - unwound reels of carbon fibre which short-circuited electrical equipment.
The US Air Force is then said to have been spurred into developing its own version of the "blackout bomb".
Stealth fighters dropped these on Serbia during Nato's military action over Kosovo in 1999.
Canisters found on the ground were labelled BLU-114/B (BLU being a standard military acronym for "bomb live unit").
The fact that they had not been used until the sixth week of the air campaign raised suspicions that they were somewhat experimental.
Pentagon spokesman Ken Bacon said at the time: "We have certain weapons we do not believe it is appropriate to talk about - and this is one of them.
He added: "It is highly classified, and it's not a weapon we choose to discuss publicly."
One of the weapon's main effects is psychological.
The then Nato spokesman, Jamie Shea, said: "The fact that the lights went out across 70% of the country shows that Nato has its finger on the light switch in Yugoslavia.
"We can turn the power off whenever we need to and whenever we want to."
The BLU-114/B is a form of cluster bomb. That is, it scatters numerous "sub-munitions" in the form of canisters about the size of a drinks can.
These in turn sprinkle highly conductive strands of carbon fibre, said to be finer than those used in the Gulf War Tomahawks.
The chances are that such graphite bombs could be used again in Iraq, 2003.