The raids, involving hundreds of armed police, were targeted at suspected republican dissidents opposed to the present ceasefire.
The dissidents are believed to be considering a new campaign of violence under the banner of a group calling itself the Irish National Republican Army.
The operation followed the discovery on Tuesday of grenades, 3,000 rounds of ammunition and three pistols in Dundalk, close to the border.
Catherine McGuinness, the Irish judge nominated by the Dublin government to chair its forum for peace and reconciliation, said she was still hopeful of an input from Unionist parties hitherto opposed to participation.
A Belfast-born Protestant, former Irish Senator and member of the Church of Ireland Synod, Ms McGuinness said she believed submissions could be made from some Unionist groups 'even though they don't feel able to become full members'. The forum is expected to hold its first session on Friday.