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2. They all built physical barriers and armies.

Recap page 177

1. They faced rivalry between kingdoms and foreign invasions.

Recap page 174

They formed a tribute system, build physical barriers , armies and developed advanced weapons.

Recap page 161

1. They all faced natural disasters.

Recap page 158

1. The people of ancient SEA faced natural disasters, succession disputes, warfare, rebellion and piracy.

Recap page 155

The ancient Chinese faced natural disasters, civil wars and rebellion.