The most advanced branch in Hittite art is architecture. The Hittite form of architecture, which is used in lower sections in Anatolia and which involves gigantic stones, continued during the New Hittite Kingdom Period. It was in 1286 BCE during the reign in Egypt of Ramses II, that war with Egypt finally broke out. Fighting took place on the plane to the south of the city of Kadesh and The Treaty of Kadesh is assumed to be the first international agreement in the history.  Internal threats, attacks by the Kashgans from the north and the Aegean Migrations of the Sea Peoples to the Levant were the main reasons for the collapse of the Hittite civilization.  Arnuvanda III did not have a child, so his brother Shuppiluliuma II become the king between the years of 1200 - 1190 BCE ans the collapse is not because of the lack of successor.