Reasons for the fall of Singapore and Malaya to the Japanese
British priority to war in Europe
British had resource constrains, such as war supplies and soldiers thus they would rather focus on war in Europe
Malaya and Singapore were not as important as they were only colonies
Germany was causing a lot of problems in Europe
British more concerned in defending and making safe their homeland
Threatened to invade and conquer England
Superior Japanese forces
Japanese had a large , modern airforce and naval fleet.
Better tactics
use of bicycles as a means of swift transport in Malaya instead of tanks
Better trained in jungle warfare
'Zero' fighter planes had destroyed half of the British planes, which were old and outdated.
British had underestimated the Japanese
Good Japanese preparations
They had signed a 'Treaty of Alliance ' with Thailand , which allowed them to land in southern Thailand
The Japanese had setup intelligence services in Malaya and Singapore to provide information on British defences and readiness
they also had operated incognito
Japanese had owned land in Singapore and Malaya , many Japanese had operated studios here. took pictures of defences and roads