The idea of an MMO RTS came from Petroglyph Games, a Las Vegas-based game developer. Sometime during 2009 pre-production began, and later Trion Worlds got on board as a publisher. The game was announced to the public at April 2010, and said to be released during 2011. This first iteration's pre-alpha footage reminded more of an MMO, rather than RTS.
The game uses (or used?) Petroglyh's in-house engine, which they used in their first game, Universe at War. Petroglyph were being helped by Trion, possibly in QA and other fields.
In August 2011, End of Nations goes free-to-play.
Later during late 2011, or early 2012 the game probably entered closed alpha phase. Around this time, beta was expected during late spring and release in summer.
Between July and November, 4 closed beta events were held, during which anyone with a beta key could participate. These events lasted 2-3 days each. This second iteration of the game was greatly different from the one in 2010. After 4th CBT event, the game was anticipated to enter Open beta phase, but that never happened. Petroglyph employees were fired, and Trion took over the development. Those who bought the game were refunded.
Currently (April 2013), according to some scarce information from Trion, the game is still being developed. Key areas are being improved and polished, using feedback from beta and alpha.