other ways; under Erishum I ( 1974–1934 BC), Assur experimented with free trade, the earliest known such experiment in world history, which left the initiative for trade and large-scale foreign transactions entirely to the populace rather than the state. Royal encouragement of trade led to Assur quickly establishing itself as a prominent trading city in northern Mesopotamia and soon thereafter establishing an extensive long-distance trade network, the first notable impression Assyria left in the historical record. Among the evidence left from this trade network are large collections of Old Assyrian cuneiform tablets from Assyrian trade colonies, the most notable of which is a set of 22,000 clay tablets found at Kültepe, near the modern city of Kayseri in Turkey. As trade declined, perhaps due to increased warfare and conflict between the growing states of the Near East, Assur was frequently threatened by larger foreign states and kingdoms. The original Assur city-state, and the Puzur-Ashur dynasty, came to an end 1808 BC when the city was conquered by the Amorite ruler of Ekallatum, Shamshi-Adad I. Shamshi-Adad's extensive conquests in northern Mesopotamia eventually made him the ruler of the entire region, founding what some scholars have termed the "Kingdom of Upper Mesopotamia". The survival of this realm relied chiefly on Shamshi-Adad's own strength and charisma and it thus collapsed shortly after his death 1776 BC. After Shamshi-Adad's death, the political situation in northern Mesopotamia was highly volatile, with Assur at times coming under the brief control of Eshnunna, Elam and the Old Babylonian Empire. At some point, the city returned to being an independent city-state, though the politics of Assur itself were volatile as well, with fighting between members of Shamshi-Adad's dynasty, native Assyrians and Hurrians for control. The infighting came to an end after the rise of Bel-bani as king 1700 BC. Bel-bani founded the Adaside dynasty, which after his reign ruled Assyria for about a thousand years. Assyria's rise as a territorial state in later times was in large part facilitated by two separate invasions of Mesopotamia by the Hittites. An invasion by the Hittite king Mursili I in 1595 BC destroyed the dominant Old Babylonian Empire, allowing the smaller kingdoms of Mitanni and Kassite Babylonia to rise in the north and south, respectively. Around 1430 BC, Assur was subjugated by Mitanni, an arrangement that lasted for about 70 years, until 1360 BC. Another Hittite invasion by Šuppiluliuma I in