|Note: The Title of This Article is Speculative|
|The title of this article and/or name of its subject matter is speculative and used in lieu of a formal and/or canonical name.|
It was following the visit of the Cetacean Probe that the Klingons chose to launch their attack. In this timeline, James T. Kirk died while attempting to rescue his son, David Marcus, from captivity under the Klingon Kruge. Thus, no attempt was made by the crew of the USS Enterprise to travel back in time so as to retrieve a pair of humpback whales who could then respond to the probe. As a result, the probe devastated Earth for a period of one week before finally leaving orbit; in the wake of its destruction, Earth and the Federation were ill-prepared to fend off an attack on the Sol Sector by cloaked Klingon ships. Ultimately, the war was fought on a broad front and with few gains made by either side. Admiral Thelin was a major player during the war and his accomplishments included winning a series of battles in the Archanis sector. Despite these victories, Earth remained under Klingon control while other key Federation planets, such as Vulcan, saw a large influx of Federation refugees. The war would end after the Genesis Device was deployed by Starfleet on the Klingon moon Praxis through Operation Olympius.
Although David Marcus had thought the Genesis Device to be a failure due to the explosion of the Genesis Planet, the Federation and Starfleet had tested it on a planet in the Terra Nova Sector with success. Realizing the implications of using the device as a weapon, David would have no part in Olympius.
During the actual operation, Admiral Thelin used a stolen Klingon ship, the IKS Katai, to travel to the Klingon homeworld. The Federation believed most Klingons on Praxis would be spared any ill-effects of the Genesis Device due to protective shields, as well as the fact that many settlements lay far below the surface. However, out of 500,000 settlers, only 2,000 survived and those who did required extensive medical treatment later on Qo'noS. David Marcus served as part of a Federation medical relief effort treating those affected by the attack on Praxis. The deployment of Genesis as a weapon led to the immediate surrender of the empire and peace talks on Khitomer. As a means for the Klingons to save face, Admiral Thelin turned himself over to their custody for having caused the death of so many on Praxis.
During negotiations, the Federation learned that, had the moon not been terraformed by Genesis, the planetoid would have been less than a year away from exploding, due to excessive mining operations.
The attack on Praxis led many neighboring powers to speak out against the conduct of the Federation; this included the Romulans, who broke off relations and stated they would develop their own Genesis Device as a means of defense against the Federation. (ST - Myriad Universes novel: The Chimes at Midnight)