The 6 Nations Agreement

Political event

The 6 Nations come together and decide to divide up the territory they've gained equally at the same time as forming a Human Confederation (which would fight itself in later years).

This is largely pushed by fears that any imbalance would mean opportunity for nations to dominate one another, leading to human vs human fighting that could weaken the race for conquest by the LIR or an uprising by the Goners. This agreement takes place on Mars, which is supposed to be symbolic of the contrast between the "builds it owns it" way that Mars was divided as the nations were actually coming together and splitting the goods evenly.