Bronze objects were exchanged into the Korean Peninsula from the outside before 900 BC. However, the moulds for bronze casting from Songguk-ri and an increased number of bronze artifacts indicates that people in the southern part of the peninsula engaged in bronze metallurgical production starting from c. 700 BC. Several hundred years later iron production was adopted, and Korean-made iron tools and weaponry became increasingly common after approximately 200 BC. Iron tools facilitated the spread of intensive agriculture into new areas of the Korean Peninsula.