I did not see the movie yet but the trailer looked awesome.
I heard some on this movie board suggest that they might be Asian but who could it be?
Why are they dressed like US SWAT team units?
North Koreans?Syrians?Iranians?Afghani? or perhaps the most logical nation that has the manpower and fleet to do so-China!
BTW Japan was on the brink of invading Australia early in World War 2.
I would go with a China/North Korea coalition. China has the means and North Korea would supply the ground forces. China would have the hardware and technology such as the advanced aircraft. During the Cold War the Soviet Union would often use Cuba as their "cats paw" to supply the troops in areas of the world such as Africa.
In reality the war would be short lived. The US/NATO/Japan would respond, end of story. Possibly even Russia responding since they do not want to see China getting any stronger.