This marks the first brigade-sized deployment from Northern Ireland on operations worldwide since World War II.
19 Light Brigade are replacing 3 Commando Brigade Royal Marines as the lead formation of UK forces in Afghanistan.
As well as Headquarters 19 Light Brigade led by Brigadier Tim Radford the units who have started deploying include 2nd Battalion The Mercian Regiment, 2nd Battalion The Rifles, 40 Regiment Royal Artillery and 38 Engineer Regiment as well as combat support troops and signallers.
The first to leave, this weekend, were soldiers from 38 Engineer Regiment who will establish base security and infrastructures for the incoming brigade. The brigade is moving into theatre by air-trooping flights direct from RAF Aldergrove over the next few weeks.
All troops have completed gruelling pre-deployment training not only in Northern Ireland but also in Germany, Kenya and Belize and, according to Brigadier Tim Radford, are "in good shape" for the tasks ahead in "trying to give a better life and freedom of choice" to the Afghan people.
Brigadier Radford takes over in Afghanistan as Commander Task Force Helmand leading the British Battle Group of around 8,000 British forces. The backbone of the deployment comprises the units under his command in 19 Light Brigade - the majority of them now based permanently in Northern Ireland.
"It has been an intensive and focused training period over the past six months and we are all now ready, willing and eager to get on with our jobs in theatre. The tour will be physically and mentally demanding. It will also be long but in many respects very rewarding. Of course we are all very aware of the dangers and threats ahead but we are also trained in how we respond and indeed deal with those threats and consequences."
The deployment means leaving their families and friends behind in Northern Ireland. Brigadier Radford continued:
"We are going to be working very hard in Afghanistan for the next six months and the support of our families and friends in Northern Ireland is vitally important to us."