In the mirror universe, Robert Wesley was a Terran male in the service of the Imperial Starfleet of the Terran Empire during the 23rd century. By 2268, he had risen to the rank of commodore and was the commanding officer of the ISS Lexington. During a war game held in that year, the M-5 computer was put in command of the ISS Excalibur. It faced off against the Lexington, ISS Enterprise, ISS Potemkin and ISS Hood. However, when it was supposed to use low-powered phasers, it instead fired on the other ships at full power, destroying the Potemkin and nearly destroying the Enterprise.