"Jock" is the callsign of an S.A.S. operative working with the AFO teams in Afghanistan as a battle casualty replacement (BCR). He was on deployment with Voodoo, Dusty and Rabbit, before the events of Medal of Honor, to recover an Afghani informant called Malouf, who had valuable intel on the local al-Qaeda HVT called Al-Zaranj.
"Jock" might be inspired by Australian 152nd Signals squadron's signalman Martin Wallace (also codenamed "Jock") who was attached to SASR during Operation Anaconda. Martin Wallace was awarded the Medal for Gallantry for his actions during the operation.