- You may also be looking for World War I.
Captain Hahn Jun-Seok speculated that according to M'Tar and Na'arbi legend, the two races were created as different ends of the spectrum and would battle until the end of eternity, and that if that legend was true, the M'Tar could have existed in a universe prior to the Big Bang.
Another legend claimed that the reason for the Big Bang was an intergalactic war between the M'Tar and the Na'arbi, one which destroyed the majority of both sides' populations and both races' home galaxies. The legend stated that the surviving M'Tar created a weapon of such mass destruction that it caused instability in the expansion of the universe, and once fired, the weapon contracted their universe at an amazing rate. This contraction and then sudden expansion created the Big Bang, and the M'Tar, as well as the Na'arbi, survivors supposedly hid in a "pocket" of space not affected by the explosion.
No known battles in the Great War had taken place up to 2372, although the minor skirmish between Hahn Jun-Seok and two M'Tar aboard the wreckage of the USS Artemis did occur around 2367. (Star Trek: The Prospect Chronicles: "Lady Lazarus")