Lieutenant Claire Westerman, 24, aims to complete 96 laps of Forward Operating Base (FOB) Shawqat in Helmand Province with two other officers, Captain Jon Toomey and Captain Greg Hutchison.
The challenge is the equivalent of a 26.2-mile marathon, and
represents training for a 350-mile endurance exercise all three will take part in next year in Britain.
Lt Westerman said: "FOB Shawqat does not have the largest amount of real estate, as we discovered when we did a half marathon in November and ended up doing 47 and a half laps.
"So come the morning of Christmas Eve, we'll not only have the cold and each other's banter to deal with, but the thought of nearly a hundred laps of Shawqat ahead of us too."
Next April, she will compete in Exercise Boru's Bound, a run from her barracks in Tern Hill, Shropshire, to Stranraer in Scotland.
From there, they will board a ferry to Belfast where they will take part in the city's marathon, all in a bid to raise more than 20,000 for the Army Benevolent Fund, the Royal Irish Benevolent Fund and Help for Heroes. Lt Westerman, from Hampshire, arrived in Helmand Province in October.