The moment President Joe Biden steps off Air Force One in Northern Ireland on Tuesday evening, he’ll be surrounded by an unusually significant security operation. Biden’s visit to this part of the United Kingdom will be short, as he will travel to the Irish Republic on Wednesday afternoon. Nevertheless, his presence is important, celebrating the 25th anniversary of the Good Friday Agreement that established relative peace between the U.K. and Irish separatist interests in Northern Ireland. Irish separatists seek the unification of Northern Ireland with the Republic of Ireland.