On Monday evening, the Defence Forces’ PC9 aircraft practised their drone interception drills over Leinster using an Air Corps helicopter as a target.
By Tuesday, road closures in the city centre hinted at a much larger no-go cordon to be put in place on Thursday and Friday.
The security operation, the largest in the history of the State, will bring parts of the city to a standstill.
The Republic took its turn at the EU presidency in July, and the final and biggest events are set to take place this week. Dublin is hosting back-to-back summits on Thursday and Friday, with up to 50 European leaders and heads of European organisations set to visit the Convention Centre Dublin and the National Gallery of Ireland.
Conor Lally, Irish Times crime and security editor, explains how the security operation will work, and what threats are feared.