Leaked change logs and second-hand testimony has been all that the public has been privileged to hear about Dota 2 until very recently, as Valve is notorious for secrecy, even more so with IceFrog serving as the lead designer. Indicators of a massive tournament and unveiling at Gamescom this year began circulating, when Valve skipped E3, but reserved space at the Cologne event, with the focus being and RTS game, something that Valve has not gained notoriety for beforehand. The most-convincing confirmation of this was a personal letter addressed to Yan Zou, a central figure to the Asian DotA scene. At long last, Valve has updated their silent and unused Dota 2 website, with the announcement of The International; the 1,000,000 USD tournament at the game's unveiling.

According to the announcement from the Dota 2 website:


The teams invited to compete include:
GosuGamers
MeetYourMakers
Natus Vincere
Invictus Gaming (ex-CCM)
Invictus Gaming Y (ex-LGD)
TyLoo
Online Kingdom Nirvana.int
Moscow Five
MiTH.Trust
EHOME
StarsBoba
Online Kingdom Nirvana.cn
Next Evolution ESC
Scythe Gaming
MUFC eSports
Mineski


Source: Dota2.com