Irish government bans Eoin O'Duffy's Blue Shirts from holding Dublin parade

The transcript describes an anticipated blue shirt parade in Dublin, highlighting the city's usual appearance despite the crowd, possibly increased by tourists. It mentions the toll on two islands and the tribute to three dead leaders. The city is under virtual martial law, with heavy police cordons blocking entrances to Leinster Lawn.

Who are the three leaders mentioned in the text, and what is their relevance?

What measures are taken to maintain order in the city during the events described?