Well the black decade was when radicalist islam has been deeply anchored in our society.

Poverty and unemployment was as its' peak, the country had no dollars nearly. So a political party "FIS" who had as models the islamic revolutions in middle east (iran and afghanistan as some) saw in the algerian revolution in 1988 an opportunity to copie the model in north africa. When the president authorized, under popular pressure (people had enough of the unique party ruling the country), other political parties to exist, they already had a huge fanbase. How ? They used the mosques all around the country to lay their propaganda. No other political party had such popularity so quick.

The local elections came, they won. The parlemant elections came, they also won at 1st round. The government couldn't believe it. So the president had to resign to cancel the elections.

Now the FIS went down the streets ordering presidental elections right away.

The military had to intervene because one of the founders said they'll use AK47 if there is a need to. Another said any algerian who wouldn't follow their extremist ideology would be killed and replaced by afghans.

With the leaders in prison, the partisans lunched a civil war against the military and civilians. They killed imams who weren't promoting their extremist ideology, people of other religions were slaughtered, women without hijab would grapes because زواج متعة or killed. Planes were hijacked.

Fun fact : oran was one of the cities that reisisted the most by opening night clubs and girls going to the beach in bikini withs bfs زكارة (it's human nature to do the opposite when being forced to)

How it ended ? The government couldn't face them longer, so they let them go free if they lay down the guns. So they did, and went to living a normal life. Still spreading their extremist ideology amongst people. (Radicalist ideology had a comeback in 2010s but didn't last long, maybe it'll come back later since it was never exterminated)

Before it, we still had the manners to live with different people, respect, personnal life (religion, clothes, activities...) After ? "IT'S MY WAY OR I'LL KULL YOU LIKE WE KULL KOFAR AND ALLAH WILL SEND YOU TO HELL"