From the introduction:
The event known as Second Impact changed everything. There isn't a person alive who didn't lose someone during the event or the chaos that followed it, and the planet itself was forever changed by the force of the explosion.
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The Second Impact was a cataclysm which followed the mysterious "contact experiment" conducted by the Katsuragi Expedition in Antarctica on September 13, 2000. While the exact details of this experiment are unknown, the result was the complete and utter destruction of the continent of Antarctica.
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The sudden, unexpected and truly devastating nature of the Second Impact threw the world into chaos. Over two billion had died in the first nineteen hours alone, and millions more were in need of crucial aid and supplies. However, the global tectonic activity had crippled nearly every nation on Earth, and systems of government around the globe collapsed under the strain.