FROM their bedrooms in Alexander House, a sheltered home for the elderly, residents witnessed six nights of street violence on July 8th-13th. Bricks, bottles and scores of petrol bombs were hurled, as police fired plastic baton rounds to try to break up crowds of up to 200, who succeeded in setting a police car alight. At one point a petrol bomb was lobbed at Alexander House itself, terrifying residents. Their misfortune is to live on a sectarian fault line in the city known to its Catholic residents as Derry and to Protestants as Londonderry.

The latest outbreak of violence, the city’s worst in several years, coincides with the emergence of a small republican dissident group, styling itself the “New IRA”, which aims to resurrect the Irish Republican Army’s campaign of violence. In Belfast, dissidents staged a drive-by bombing on July 13th of the home of Gerry Adams, a former leader of Sinn Fein, the party which once functioned as the IRA’s political wing. No one was hurt.

The New IRA, which has only a few dozen members and a handful of leaders, regards the peace process as a betrayal of republican ideals, and condemns Mr Adams as a traitor for his part in it. In Derry, where the recent violence has been concentrated, one dissident opened fire with a machine-gun on July 10th. Others have been surreptitiously active in the city’s poor Catholic neighbourhoods, teaching youths the art of making petrol-bombs and lobbing them at police vehicles.

Police report that children as young as eight have been involved. Both officers and community leaders accuse the New IRA of taking advantage of children, who are off school for the summer holidays. Few minors have been hurt in the past week’s violence, but some have been arrested and are likely to end up with criminal records.

There is a dismaying sense of déjà vu. Decades ago one such youngster was Martin McGuinness, who graduated from Bogside brawling to become one of the IRA’s most feared leaders. He later recalled: “Like everybody else I threw stones and whatever else was to hand at the RUC [the police]. People saw me as someone who was prepared actually to be within ten feet of the RUC and the British army and throw stones.” He went on to play an important part in the peace process that dissidents now aim to destroy.

Could all this signal a revival of the Troubles of 1968-98, which led to more than 3,500 deaths? Community relations are fractious, with Northern Ireland’s political parties so far apart that its Assembly has been closed for more than a year. Brexit has caused fresh divisions, pitting the British and Irish governments against each other and raising fears that a hard border could return.

Yet the fresh eruption of fighting has produced an unusual example of political unity. The five main political parties combined to denounce “such disgraceful violence” as “a clear and obvious attempt to murder police officers”. This is language not usually heard from Sinn Fein, whose new leader, Mary Lou McDonald, described the dissidents as “warped, negative, regressive, dangerous people”. And in another small but encouraging sign that history need not repeat itself, an anti-violence rally was attended by Fiachra and Emmett, two sons of Martin McGuinness. Its theme was “Not in our name”.