An international coalition formed by the PLANT sponsor nations and their terrestrial allies to battle the forces of ZAFT. The Earth Alliance is not a single political entity, but rather a collaboration between several individual nations, which regard each other as potential adversaries even though they are currently united against a common foe. The dominant powers within the Earth Alliance are the Atlantic Federation, the Eurasian Federation, and the Republic of East Asia, all three of which invested heavily in the construction of the PLANTs. The South African Union and the United States of South America are junior partners in the Alliance, with the latter having been forcibly annexed by the Atlantic Federation at the start of the war.
The Earth Alliance was formally established on February 7, C.E. 70, two days after final negotiations between the PLANTs and the sponsor nations were disrupted by a terror bombing at the lunar city of Copernicus. The Alliance was created as a successor to the former United Nations, whose leadership was wiped out in the Copernicus attack, and like its predecessor it's nominally an international organization headed by a moderate secretary-general. However, in practice it's little more than a military alliance dominated by the Atlantic Federation and its fellow PLANT sponsor nations.
The military forces of the PLANTs. ZAFT is a militia made up of civilian volunteers, and the organization has no formal rank structure, so its members are instead addressed by descriptive titles like "commander" and "captain." The ZAFT forces are organized into independent teams named after their commanders, and much like the modern-day U.S. Marines these teams can operate equally well on land, at sea, in air, or in outer space. Since ZAFT's membership is made up of genetically enhanced Coordinators, its forces are more than a match for the numerically superior Earth Alliance.
ZAFT was originally a political organization called the Zodiac Alliance, which was founded in C.E. 50 by Siegel Clyne and Patrick Zala. The Zodiac Alliance took on its present name in C.E. 65, and three years later it was reorganized to become an explicitly military organization equipped with the revolutionary new weapons known as mobile suits. The ZAFT forces are currently subject to the authority of the PLANT Supreme Council, and report directly to the National Defense Committee.