Also known as the Three-Way War, and by other titles, this was a major conflict in September 2013 during which certain powerful nations from Nation Creation invaded Create Your Own Country. At the same time, the Portal Nations also invaded CYOC, thus the Dual in Dual Invasion.
Nation Creation's reason for getting involved was Eno Remnant's concern that CYOC had become a dying game, and that its rules needed fixing if the game was to be revived. Thus, he contracted the assistance of a handful of nations from NC, and a smaller number of sympathetic CYOC nations.
The reason of the Portal Nations seems to have been to produce some kind of activity in the dying thread, in line with Eno's own beliefs.
It ended with an agreement between Kyr, Eno and Sith to revise the CYOC system. These changes were implemented to much positive effect.
The nations of Nation Creation entered the CYOC universe through a rift 'accidentally' opened by the Ascendant Kingdom/Twin Gods' Empire. At their vanguard were The Conjoiners (under Wayne), who quickly attacked Earth with the assistance of the Twin Gods' Empire, who deployed Alar and Trickster fields around the Earth to prevent entry and escape to the various CYOC forces.
After interference by the Portal Nations, more fields were generated around every planet, to ensure there would be no interference.
After the interference of the Portal Nations was dealt with, Godking Marcus addressed the following terms to CYOC countries:
ATTENTION, ALL CYOC NATIONS:
By order of Godking Marcus, head of the Crusade against the Big Five, you will now surrender to Crusader forces or be destroyed.
We shall not falter in our attempts to fell you until such a time as our terms are met:
1) The Age/Power equivalency rule shall be struck, or heavily reduced.
2) A new BoSS shall be selected from current active nations.
2a) An election system shall be installed to ensure inactive BoSS members are replaced by active players.
3) A number of non-BoSS moderators shall be drafted from current active nations to provide more direct, less lengthy moderation on wars and technology.
4) All countries with a ranking shall be stripped of it, and be required to earn their ranking based on their country's merits, not on its age.
Should all of these terms be met, there shall be no further aggression.
Following this, the Oceani-Zargarian Empire (under Kyr) passed through the rift to join the invasion.
The invasion then ended with an official notice from Godking Marcus, pending the installation of a new system created by Sithlord Man based on Eno's terms.
A number of nations from another universe entered CYOC through a portal, planning their own invasion at a coincidentally similar time as the Ascendant Kingdom began Operation Ending Crusade (the project which opened the rift).
The Portal Nations were caught up in Nation Creation's invasion, and fought with them briefly, before they signed the Treaty of Three Sides.
Upon the cessation of hostilities, the need for a revised treaty was made abundantly clear.