The first contingent of Irish peacekeeping troops will deploy to Lebanon overnight.
The 200 members of the Defence Forces will depart in the early hours of Thursday morning.
Patrolling a 140km sq area, the soldiers have been sent to protect civilians and ensure humanitarian supplies reach them, as well as help Lebanon's armed forces.
Another 220 members of 104th Battalion will go to Lebanon at the end of the month to join the United Nations Interim Force in Lebanon (Unifil).
The youngest soldier of the group is 20-year-old Private Emma Furlong who grew up at the Curragh where her father Daniel is still based.
An advance party of 90 specialists has been in Lebanon since the end of May, preparing camp and infrastructure for the battalion in the southern village of Tibnin in Bint Jbeil, and two smaller posts along the so-called blue line with Israel.
Irish officers were first sent to Lebanon, as observers, in 1958. The first battalion was there from 1978, as part of Unifil, when Israel invaded the country. Since then 47 Irish troops have been killed in Lebanon.
The main Defence Forces battalion was withdrawn in 2001 after 23 years but was deployed again in 2006 for 12 months. The current mission is expected to last as long as four years.