The Seven Days was a widespread riot during Anno 275 NP.
The exact events that lead to The Seven Days is somewhat unclear. It is believed that a peaceful protest during The Closed Gates grew in size enough to pose a threat to the inner city. The City Guard opened fire into the crowd, escalating the protest into a riot.
The people grabbed whatever they could and began to form makeshift ladders up the walls of Tier IV. Each wave was repelled by the City Guard, who slaughtered all those attempting to break through.
The riot was over in seven days, by then nearly ten thousand civilians and several hundred guards had been slain.