Some of the soldiers who trained and served with Harry in the UK and Afghanistan will have "pride of place" outside St George's Chapel, in Windsor Castle as the royal newlyweds emerge.
More than 250 members of the armed forces will perform ceremonial duties at the wedding on May 19.
Twenty-three soldiers, one sergeant and one officer from Harry's former Army Air Corps regiment will line the street outside the chapel where the royal couple will say their vows.
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The prince, known in the Army as Captain Wales, served with 662 Squadron, 3 Regiment Army Air Corps as an Apache helicopter pilot in Helmand Province in late 2012.
Captain William Calder, who will be half company commander on the day and lead his soldiers in a royal salute, said he had some nerves ahead of the big day.
He said: "We will march through Windsor into the castle in time for the end of the wedding and as the couple and the royal family depart, we will be pride of place presenting them with a royal salute as they emerge from the chapel.
"It makes me a little bit nervous that we will be front and centre - the Queen and the senior members of the royal family will be stepping out the door right beside us and I'll probably be positioned about five metres from them."
Capt Calder, 32, who has dual UK/US citizenship, said his unit would be training hard ahead of the wedding and he reacted with "stunned surprise" when he found out he would play such a key role.
He added: "This is absolutely not our normal business, we are an Apache regiment, we fly Apaches for a living and we are very operationally focused most of the time.
"For us stepping into ceremonial duties is something a little bit outside of our remit but it's a nice, special treat and something different."
Having been born in New York before moving to the UK at the age of seven, Capt Calder said his family on both side of the Atlantic were looking forward to the nuptials.
"Understandably, my family are pretty excited," he said.
"I've got a lot of family in the US, who somehow seem to be much more excited even than the British family members.
"So I think I will have loved ones keeping an eye on me all across the world, for better or worse.
"I think even the American ones will be waking up early to keep an eye."
Capt Calder said his only meeting with the prince was a chance encounter at the cafe at Army Aviation Centre at Middle Wallop, in Hampshire, where the royal asked him "Can I join you?"
"I knew he looked familiar, finally it dawned on me it was Prince Harry and of course he was utterly natural and charming and friendly and just like any other officer in the regiment," he said.
Another soldier who served with the prince during his time at Wattisham, Staff Sergeant North, said he too harbours a few nerves but he was confident the half company would be ready.
"It's a privilege," he said.
"Obviously there will be a few thousand people in attendance and millions of people worldwide watching the event but to be one of the roughly 250 military personnel taking part, to be able to see it will be amazing.
"There's always going a little bit of nerves and trepidation with anything you do to that level but by the time we get there, the training we conduct this week and next, we'll be looking smart and good to go."
The 35-year-old, whose first wedding anniversary is the following day, will have to miss part of his daughter's fourth birthday to perform his duty.
He said she was "delighted" her father was involved and she would probably watch a recording of the event later.
"I get to miss the soft play but I will be home in time for bedtime, which is the most important part and in time for the presents," he said.
Corporal Stuart Armstrong, 27, a communications specialist who worked with Harry "day-to-day" during Apache training, said it was an "honour" to be nominated and the soldiers had been busy preparing.
He said: "We've been at it all week this week, so between practising our drill, getting our uniforms ready so it's been pretty much non-stop all week."
He said the prince had been "just like another officer".
The AAC soldiers selected practised their drill in the sunshine at a windy Wattisham Flying Station, in Suffolk, on Thursday.
They paraded and gave the royal salute in their dress uniform, known informally as "blues", with a red stripe down each leg and sky blue beret.
Joining them will be a half company of 25 personnel from RAF Honington in Suffolk, where Prince Harry is Honorary Air Commandant.
The selected group will form a guard of honour during the royal wedding carriage procession.
They conducted uniform inspections, foot drills, rifle drills and sword drills as part of their preparations on Thursday.
Sgt Adrian Dixon, who is in the RAF Police stationed at Honington, said taking part would be the "highlight of my career".
"Prince Harry was serving in Afghanistan at the same time as I was and I often wonder was he up overhead in his Apache as I conducted my patrol," he said.
"He was there for me when I needed him, now I can be there for him on his special day."