Liam McDonnell was into soldiering from his early teens, though he didn’t quite express it that way back then.

Before he joined the Defence Forces aged 20, he was 10 years in the boy scouts, hoovering up badges and taking every challenge on offer – including the Peak Challenge and the Chief Scout Award. Scouting “really got my hunger for an outdoor life,” he says.

When he finished school, he worked on building sites for a year before he applied for an Army cadetship and succeeded – on his second try.

“My mother burst out crying when I told her I’d joined,” he recalls.

Today, he is a total soldier, utterly engrossed in his work, committed to it and loving every day of it.

“He absolutely loves it and he’s really looking forward to heading off,” says his partner Mel, a primary school principal in Killimor, Galway. “For the last few months, he really wanted to go on this mission and he would have been devastated if he hadn’t been able.”

Promoted from lieutenant to captain last June and a veteran of the United Nations Interim Force in Lebanon (Unifil), McDonnell learned only in mid-February that he had been selected for the United Nations Disengagement Observer Force (Undof) mission to the Golan Heights.

“I was about four weeks after everyone else. There was a dual qualification required for my position and there was no one qualified to go out originally. And the only people who have them in the Army right now are commandants because of all the promotions. I only got promoted from lieutenant last June.”

McDonnell’s role as company second-in-command, or 2IC as it is expressed in the military, will involve him working closely with the Group 2IC, Comdt Paul Kelly, and Sgt Maj Noel O’Callaghan, but relating mainly “down the line” to the other ranks.

“I have to make sure that every element of the company is ready for combat deployment. So if the company commander wants to mobilise his full company, he tells me two days beforehand, ‘we’re going on an operation’ and it’s my job to get that company ready. I’m the guy behind, pushing everybody forward, making sure the standards are kept.”

McDonnell is highly trained and highly skilled – in some things hopefully his troops won’t have to use, but will be thankful for if they do. He is a serious fitness enthusiast, map-reading instructor, sniper instructor in advanced marksmanship (and coach to Defence Force participants in international competitions), anti-armour instructor and a reconnaissance commander.

He has also taken survival courses and used knowledge gained during a day’s survival training for others predeployment.

The training involves unarmed combat and how to disarm an opponent. “The thumb is actually quite weak,” he notes. “By pushing against it and whatever they are holding will fall from their hand because it is almost impossible to maintain a grip on something with fingers only.

“If a weapon is pointed at you, it is easy and fast to push it to one side, or side and up. You look directly in their eyes and you won’t give anything away and it’s just, straight away [sweeping movement of his arm] and it’s done.”

If alone in enemy territory, maps drawn on cloth and sewn inside clothes, a button-sized compass secreted on the back of an actual button, and a piece of flexible reflective plastic could make the difference between being seen and not, between surviving and not.

The advice is to move slow and steady.

“The difference between a soldier and a civilian is a soldier doesn’t want to be caught and a civilian wants to be found,” says McDonnell. “A civilian will walk through the daylight to make sure he is clearly identified so anyone can see him whereas a soldier has to move at night time so he doesn’t get himself into another situation that is worse.”

Worse is being caught or abducted, which has happened to Undof personnel. Co-operate but be a “grey man”, says McDonnell.

“You can’t just sit there and say nothing because then you are invaluable to them. They don’t know who you are, they don’t know what they’ve got. You have to give them something,” he says.

At the same, if you are in a group or of senior rank, don’t stand out.

“You are a grey man the whole time. You don’t try to be brave; you don’t try to be robust or aggressive. You just sit there, the grey man in the background and if there are other people there, everybody’s the same because if someone stands up and thinks ‘I’m in control here’, you’re identified as a leader and they’re going to take it out on you and their interrogation is going to be considerably more robust.”

Perhaps not surprisingly, when relaxing with Mel, a certain amount of walking can be involved.

“He’s got me into that – long walks and hikes,” she says.

They are both aged 31 and met 3½ years ago in Busker Brownes in Galway. In 2013, they had a special holiday in Banff, Alberta, Canada, a city near Sulphur Mountain (2,281m) that may be conquered by cable car .

“Oh my god!” said Mel. “Most normal people would get a gondola up to the top of it but no, Liam decided we were walking up this mountain and there was no straight part of it the whole way up.”

“It was tough,” he concedes.

“And he kept feeding me sweets the whole way up to keep the sugar levels up. But it was worth it.” she admits.

Mel is not overly worried about the mission, more anxious. “Liam doesn’t tell me all the information but then I start looking things up, that I shouldn’t be looking up, on the internet because it never looks good . . .”

They will miss each other.

“I’ve been expecting it for a while,” says Mel. “He’s been talking about it for so long that I got my head around it. I’ve been talking to a lot of other people who’ve been through it and they say the first few weeks are the hardest but then after that, it’s the countdown for him coming home on leave.”