On 6 March 1944 the Australian Government and military received an incorrect report that two Imperial Japanese Navy

Imperial Japanese Navy

The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

 battleship

Battleship

A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...

s had entered the Indian Ocean

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

, possibly to attack Fremantle

Fremantle, Western Australia

Fremantle is a city in Western Australia, located at the mouth of the Swan River. Fremantle Harbour serves as the port of Perth, the state capital. Fremantle was the first area settled by the Swan River colonists in 1829...

 and Perth

Perth, Western Australia

Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....

. In response, the Allied

Allies of World War II

The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 forces in the state of Western Australia

Western Australia

Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

were rapidly reinforced. The threat of attack rapidly passed and the Allied naval units returned to their normal dispositions on 13 March followed by the air units a week later.