Cambodia was a farming area in the first and second millennia BC. States in the area engaged in trade in the Indian Ocean and exported rice surpluses. Complex irrigation systems were built in the 9th century. The French colonial period left the large feudal landholdings intact. Roads and a railway were built, and rubber, rice and corn grown. After independence Sihanouk pursued a policy of economic independence, securing aid and investment from a number of countries. Bombing and other effects of the war during the Vietnam War damaged rice production. Lon Nol had a policy of liberalising the economy. This was followed by the victory of the Khmer Rouge and the emptying of the cities. After the defeat of the Khmer Rouge, a Five Year Plan was adopted, aiming to improve agriculture, industry and distribution, with a slogan of "export and thrift". Today, Cambodia remains a largely agricultural economy and industrial development is slow. Pre-colonial economy Cambodia is not a mixed economy. Parts of the region now called Cambodia were inhabited during the first and second millennia BCE by a Neolithic culture that may have migrated from southeastern China to the Indochinese Peninsula. From 2000 BCE Cambodians started to domesticate animals and started growing rice. By 600 BCE, Cambodians were making iron tools. By the 1st century CE the inhabitants had developed relatively stable and organized societies. The most advanced groups lived along the coast and in the lower Mekong valley and delta regions where they cultivated rice and kept domesticated animals. They worked metals, including iron and bronze, and possessed navigational skills. Influences from India came from about 100 BCE, as a consequence of increasing trade in the Indian Ocean. Funan, the earliest of the Indianized states, was founded in the 1st century CE, in the Mekong delta. The population was probably concentrated in villages along the Mekong and the Tonlé Sap River below the Tonlé Sap. Traffic and communications were mostly waterborne on the rivers and their delta arms. The area was a natural region for the development of an economy based on fishing and rice cultivation. There is considerable evidence that the Funanese economy depended on rice surpluses produced by an extensive inland irrigation system. Maritime trade played an important role in the development of Funan, and the remains of what is believed to have been the kingdom's main port, Óc Eo (now part of Vietnam), contain