The Wessex Cup is an annual event which sees the Countess' regiments and military organisations compete against each other in a series of challenges.
Countess Sophie also joined in to play a racing game which was part of the E-Gaming Challenge.
Flight Lieutenant Sam Lawton, an RAF engineer and project officer for the 2021 contest, said: "If there was a competition for the military in the 21st century, this is it.
"There is a tough physical event, but we've also included an escape room, a media challenge, science and engineering, and even an online gaming element. It's all there."
The Countess is the Honorary Air Commodore for RAF Wittering near Stamford, and has formal links to several other military bodies.
She is Colonel-in-Chief for Queen Alexandra’s Royal Army Nursing Corps, and the Corps of Army Music; the Royal Colonel of 5th Battalion The Rifles, and the Lady Sponsor of HMS Daring.
The Countess is also the Colonel-in-Chief for two Canadian regiments: the South Alberta Light Horse and the Lincoln and Welland Regiment.
5th Battalion The Rifles secured victory for the Army in this year's The Countess of Wessex Cup.
Wing Commander Jeremy Case, Station Commander at RAF Wittering, said: "The atmosphere has been one of cooperation and friendly competition, a valuable part of life in the Armed Forces that helps foster esprit de corps.
"Our project officers have done a great job in designing and organising today's event which was enjoyed by all, including Her Royal Highness."
Cover image: The Countess of Wessex takes on the E-Gaming Challenge during her visit to RAF Wittering (Picture: PA Images / Alamy Stock Photo).