With the exception of the Evangelion Units, N² Weapons are the most advanced and destructive weapons developed by mankind. An abbreviation for Non-Nuclear, these weapons are in the arsenal of both the U.N. Forces and the Strategic Self Defense Force. N² Weapons come in several varieties, including N² mines, N² depth charges, N² aerial mines, and N² bombs.
N² Weapons were successfully deployed against Sachiel, the Third Angel, and Israfel, the Seventh Angel. Although they were inadequate to destroy these targets, their sheer power was enough to damage them, something that no conventional weapon could do. Towards the end of the series the Angels grow increasingly more powerful (such as Zeruel, the Fourteenth Angel), and even a close range detonation of an N² mine by Evangelion Unit-00 has no effect.
In The End of Evangelion, the Strategic Self Defense Force deploys N² Weapons to destroy the entirety of New Tokyo-3 and the Ceiling City in their efforts to claim Special Duty Organization NERV and prevent the Third Impact. They fail.
Based on Neon Genesis Evangelion Platinum: 05 DVD Booklet