The Lae and Salamaua Landings

Two main sea routes were available for this traffic, and were used according to prevailing weather conditions. Other things being equal, during the south-east season from mid-April to October, the choice naturally fell on the route between Rabaul and Lae by the south coast of New Britain, since at this time a bank of thick weather extends along the coast to a distance of 50 to 75 miles. On the other hand, during the north-west monsoon season from December to the end of March areas of thick weather cover the north coast route, through the Vitiaz Straits, while clear weather makes conditions on the southern route favourable for attack.

In this manner, by careful use of forecasted deteriorations in weather conditions, convoys could be sheltered over most of the route by cloud, rain areas and squalls, and our enemies made able use of the meteorological factor to keep their garrisons supplied.

As Allied air and sea strength assumed greater concentration at this point, however, the journeys increased in hazard for the Japanese. During 1943, for instance. Allied aircraft sometimes picked up enemy convoys near Rabaul and, by utilising occasional breaks in the cloud cover, attacked the ships throughout their outward journey, during the discharge periods at Lae and also on the homeward run.

By mid-September 1942 both Lae and Salamaua had fallen to the Allies, and then commenced the series of assaults that were to carry Allied forces to Borneo and beyond. In October our land forces captured Finschhafen and set out for Madang, the RAAF meanwhile carrying on an air offensive against New Britain which succeeded in virtually isolating Rabaul and smashing the enemy's system of sea communications around New Britain. Thereafter, for the Japanese, even skilful use of the weather factor was insufficient to keep convoys moving; only desultory traffic was possible and for the most part that proved very costly.

Bureau of Meteorology