The Great Resettlement

Item from deaths-end by Liu Cixin

The Trisolaran-enforced relocation of all 4.5 billion humans to Australia in the days after deterrence collapses — the worst hour of the species.

What They Know

All 4.5 billion humans on Earth are forced onto the Australian continent within weeks
Small reservation populations are also tolerated on Mars and the Moon
Anyone violating the deadline is killed by droplet strike from orbit
All Australian electrical and food infrastructure is destroyed once relocation is complete
Sophon predicts and engineers a population collapse to ~200 million through cannibalism
Ends with the Broadcast Era — the broadcast forces the Trisolarans to abandon Earth occupation