What exactly is Crysis about?

There are currently three versions of Gudao, and naturally the strategies and plots are all different.

The original version of Gu Island 1 is about the discovery of a strange phenomenon on an island in the Pacific. The United States dispatched nano-armored special forces to the island to investigate, but the North Koreans had already sent troops to the island first, so they attacked the North Koreans first and then Halfway through, I discovered that the strange phenomena were caused by aliens, and the aliens had already begun to attack, so they attacked at the same time and finally attacked the alien mothership

Crysis: Warhead, this version is sometimes mistakenly called Gu Island 2 is actually an expansion pack for Gu Island 1. It is based on the teammates of the original protagonist. It tells about the situation he encountered on the island, which basically happened at the same time as 1

Gu Island 2 , this is the latest, aliens have begun a full-scale attack, attacking and colonizing major cities on the earth. The guy who was the first to translate Crysis, a name that has nothing to do with the island, into "Crysis" just for convenience, now finds himself in 2B. This version is not an island but takes place in a city in the United States.

So if there are no Koreans, we are fighting aliens