Traditionally, located in the shallow waters of the Persian Gulf, the Iranian navy has always been the smallest of its military forces. An Iranian navy in one form or another has existed since Achaemenid times in 500 BC; however, except for the Achaemanid navy, none of the following navies were particularly well organised or strong. It was only with the Pahlavi dynasty in the 20th century that Iran began to consider building a strong navy to project its strength into the Arabian Sea and Indian Ocean. In more recent years, the country has engaged in domestic ship building industries in response to the western-backed first Gulf War (also known as the Iran-Iraq war), which left it without suppliers during an invasion.