The Iranian Navy traditionally located in the shallow waters of the Persian Gulf, has always been the smallest of the country's military forces. An Iranian navy in one form or another has existed since Achaemenid times in 500 BC. The Phoenician navy played an important role in the military efforts of the Persians in late antiquity in protecting and expanding trade routes along the Persian Gulf and Indian Ocean. With the Pahlavi dynasty in the 20th century that Iran began to consider building a strong navy to project its strength into the Persian Gulf and Indian Ocean. In more recent years, the country has engaged in domestic ship building industries in response to the western-backed Iraqi invasion of Iran, which left it without suppliers during an invasion.