The decision to change the threat level to “severe,” meaning an attack is highly likely, was made by the UK’s MI5 security service and announced by UK Secretary of State for Northern Ireland Chris Heaton-Harris on Tuesday.

Heaton-Harris said the move was made after an increase in “activity relating to Northern Ireland-related terrorism” including the attempted murder of a high-profile police officer last month. While the public should remain vigilant, they should not be alarmed, he said. …

The change in the threat level comes weeks before a possible visit to Northern Ireland by US President Joe Biden to mark the 25th anniversary of the Good Friday Agreement (GFA), also known as the Belfast Agreement, which brought an end to decades of sectarian violence between Irish republicans and unionists known as “The Troubles.”

[This isn’t so much about the GFA as it is about the tensions surrounding Brexit. The trade issue threatens to reimpose a hard border in Ireland; that and the attempts to avoid that outcome have ramped up bitterness over national identity in both sides of the century-long crisis in Ulster. This was a predictable outcome of Brexit, and the lack of any real effort to address it prior to executing Brexit is amazing in retrospect. — Ed]