[Shivetya]

One of the best series exploring this area is the http://en.wikipedia.org/wiki/Lensman series. Weaponry was only useful; not obsolete; up until the enemy found out about it. In the environment he created you could pretty much negate or create something once you knew it was possible. As such they went to great extents to keep things secret.

In the end, the final solution was crashing light speed plus planets from alternate dimensions into your target planet, bonus points for negative matter planets

Anyone interested in science fiction should read these books but realize that they are a product of their time and it may offend the sensibilities of some readers.