The following events took place in 2157 CE, or Common Era.
- Turians discover human explorers attempting to reactivate Relay 314 and open fire, inadverdently starting the First Contact War. The brief war results in humanity entering the galactic community. Many Alliance Military officers, however, are stung by the defeat, and the Office of Alliance Territorial Hegemony is established to protect Alliance interests.
- 7th Naval Battalion is formed.
- Snovaco begins rounding up all children born on its Segonia settlement on Cailloux, including Emmanuelle Sharon and Tereza Kodetovic, gathering them together once a week for physical examinations. This continues every week until the settlement's destruction in 2170 CE. The purpose behind these examinations, collectively dubbed the "Segonia Project" by conspiracy theorists, is never revealed, but inspire a number of conspiracy theories.
2156 CE - 2157 CE - 2158 CE