In 2372, after a Changeling bombing on Earth, Admiral James Leyton imposed martial law and tried to seize power until Sisko exposed him.
In 2372 a bomb at a diplomatic conference in Antwerp killed 27 people, and evidence pointed to a Changeling. Sisko was called to Earth to help with security, and blood screenings and phaser sweeps were introduced to detect shapeshifters. When Earth's power grid suddenly failed, the Federation President declared a state of emergency, and Starfleet troops were deployed on the streets.
Sisko learned that the blackout had been caused by officers loyal to Admiral James Leyton, his former commanding officer, who wanted martial law in order to put Starfleet in control of Earth. Leyton used the cadets of an elite Academy group, Red Squad, to carry out the sabotage. A Changeling who had taken the place of O'Brien told Sisko that only a few Founders were on Earth, and that the fear they caused was enough.
Sisko confronted Leyton and was attacked by the USS Lakota while the Defiant brought evidence to Earth. Once the plot was exposed, Leyton resigned, and the emergency ended.