YDT 2021-1 Soru=37

What is the passage mainly about?

Around 1650 BCE, central Anatolia’s city-states were
united by conquest into a kingdom with its capital at
Hattusa. Vigorous rulers of this Hittite Old Kingdom
campaigned into Syria and even sacked Babylon in
1595 BCE. However, the series of succession disputes
that followed reduced their dominions. From the 14th
century BCE on, strong Hittite kings regained previously
lost territories, expanded into western Anatolia, and
destroyed the Mitanni Empire in Syria, thus bringing
them into direct territorial competition with the
Egyptians. After the inconclusive Battle of Qadesh
around 1274 BCE, Egypt accepted Hittite control over
Syria. Widespread human and natural troubles in the
eastern Mediterranean around 1200 BCE destroyed the
Hittite Empire, but a number of small Neo-Hittite
kingdoms sprang up in southern Anatolia and Syria,
prospering until the Assyrians conquered them in 700
BCE. Barbarian raiders ever present to their north and a
tradition of armed conflict made the Hittites invest
heavily in defence. Massive and complex city
fortifications included towers, huge stone gateways with
difficult approaches, and long tunnels under the walls to
secret exits. Often a citadel and inner defensive walls
protected the palace and other key buildings