At least to my knowledge nothing like this has occurred in over fifty years. "In time of peace, prepare for war."
American military "testing" the USA populace as a means of evaluating civilian response to a stressful and wartime situation.
UNANNOUNCED POWER-OUTAGE SIMULATING A CYBER-ATTACK BY A FOREIGN POWER HOSTILE TO THE UNITED STATES. POWER GRID INTERFERED WITH. VITAL ENERGY NOT FLOWING.
Thanks to the Charlotte Observer and the article by MARK PRICE.
"Fort Bragg cut power for thousands to test ‘real-world reactions’ to a cyber-attack"
"Fort Bragg in North Carolina says the Army base had a 'blackout' for more than 12 hours overnight Wednesday as part of a cyber-attack military exercise that came as a complete surprise to its tens of thousands of residents."
Unanticipated and unannounced.
From over fifty years ago see this You Tube video the Sonic Boom Tests [Bongo]. American warplanes repeatedly making supersonic passes over Oklahoma City USA, the citizenry and structures evaluated with regard to response to sonic booms and damage as caused by same. Believe me, these sonic booms quite loud and startling.
NOT ONLY Oklahoma City, USA. Chicago Illinois, USA also subjected to repeated sonic booms from high-flying B-58 Hustler Strategic Air Command bombers flying out of Bunker Hill AFB. I remember these night-time sonic booms well, as if it were yesterday. Reaction of the public deemed inappropriate. Persons running out-of-doors to determine the source of the house-rattling "boom". During a time of global thermonuclear war such a sonic boom might precede the detonation of an atomic weapon. So was the thought.