It is an annual convulsion of violence. Every summer when marching season begins in Belfast, violence flares between the Northern Ireland capital's Catholic and Protestant communities. This week, the unrest has been particularly intense, with 80 police officers having been injured in four nights of rioting. Still, Belfast police said on Thursday that violence appears to be dying down after a relatively calm Wednesday night. Much of the recent violence has been blamed on factions who oppose the Good Friday peace settlement of 1998, which sought to reconcile Northern Irish Catholic republicans with Protestant loyalists.