The Na'kuhl were an alien species from Enterprise who were once engaged in a Temporal Cold War but became corrupt due to the influence of the fanatic known as Vosk, who believed time-travel was his birthright despite the potential harm it could do to time-lines.
At one point in their history under Vosk's leadership, the Na'kuhl attempted to eradicate the Suliban. They traveled into the past to prevent the Suliban from becoming sentient. However, an opposing faction of temporal agents stopped the Na'kuhl and ensured that the Suliban attained sentience, despite the ongoing enmity between the Temporal Agents and the Suliban.
The Na'kuhl were very nearly defeated and captured by Daniels' faction, but managed to develop a type of stealth time travel before they could be vanquished. This innovative device had the drawback of allowing only one-way travel. Using the device, the Na'kuhl escaped to Earth in 1944 of an alternate timeline created by multiple temporal incursions from the different factions. In this reality, with the assassination of Vladimir Lenin by an unknown faction, Nazi Germany had been able to concentrate solely on the Western Front during World War II, allowing Adolf Hitler to quickly take over England and then much of the eastern coast of the United States, including New York City and Washington, DC. The Na'kuhl were allies to the Nazis and were granted ranks in the SS, complete with the "privilege" to wear SS uniforms as well as several Nazi medals.