RAAF Radar Station No. 313 was located at the southern end of Mornington Island in the Gulf of Carpentaria. Flying Officer R.J. Brown and 35 RAAF personnel were attached to this Radar unit. There was a small new airfield adjacent to the Radar Station for the delivery of supplies, etc.

In about November 1943 spurious radar echoes were recorded circling a section of the island about 10 - 15 miles north west of the Radar Station. An investigation to identify the aircraft proved inconclusive. On 14 January 1944 the on-duty crew at the Radar Station detected another single unidentified aircraft circling in the same area.

On 15 January 1944, the local Aborigines reported seeing a large black ship attempting to land on the beach about 15 miles north west of the Radar Station. After four unsuccessful attempts the ship headed for nearby Rocky Island. 

Flying Officer Brown and Warrant Officer Dunlop investigated the area and no trace of the ship or any other sign of a landing could be found. The aborigines said that they had been attracted to the area by the sounding of the ships' boat horn. Flying Officer Brown established pairs of aboriginal lookouts about 5 miles apart along the coastline in an attempt to sight the intruders.

At sunset on the 16 January 1944 a surface vessel was plotted on the radar screen. It moved from Rocky Island to a position about 10 miles off the coast from the Radar Station. As it was heading directly towards the Radar Station a blackout was observed and defensive positions established in case of an enemy landing. After an uneasy night, no trace was found of the intruders the next morning.

Flying Officer Brown and a small party of men climbed a high peak on Mornington Island to observe Rocky Island. Again there was no evidence of the intruders. After this incident machine-gun emplacements were built and the RAAF personnel carried out regular rifle shooting training on their 200 yard target range.

These suspected landings on Mornington Island and Rocky Island coincided with a confirmed Japanese landing on the West Australian coast near Cartier Island and Browse Island.