System Defense Treaty (SDT)

General
The Inner System Defense treaty (ISDT) was an alliance created by the factions of Terra, Luna, Venus, Mercury and Ceres during the First Colonial War of 2238. The alliance was created as a form of protection from the disgruntled outer planets who were trying to declare their independence from Earth. In response to sanctions, suppression and general inequality set by the inner planets, the outer planets declared independence from Earth and inner planets forming the Colonial Expeditionary Pact (CEP).

Formation
The Inner System Defense treaty (ISDT) was formed after increase pressure on the outer worlds made them declare their independence. As a result of this unification, Earth formed the ISDT, becoming the first planet to sign the treaty. Luna, who was an independent state but worked closely with Earth, became the second to sign the treaty. Mars became the third to sign the treaty. Ceres, an important resource hub for the inner planets, joined later as the fourth to sign the treaty. Venus, an important research colony, became the fifth to sign while Mercury, an important military hub for the inner planets, became the sixth to sign.