The Japanese highly relied on imported fuel to run her military operations in China. The USA and the British chose to put an embargo to the importation to sabotage Japanese operations in China. That did not go down well with the Japanese and they began the attacks including the Indochina and the Eastern Asia where the Allied had interest.
The Malayan campaign was one of the after effects of the sanctions put on Japan. They invaded Malaya on 8th December 1941 during the Second World War. It is within this period that they also invaded Indochina, Burma, and Singapore.
On the other hand, the British had the Commonwealth forces to fight against the Imperial Japanese Army. This attack, and defense of the Malaya is what is referred to as the Malayan Campaign. However, the Japanese seemed to have made a very strong build up at Singapore and Thai that made their invasion in Malaya swift.
The imperial Japanese Army moved on bicycles that made the advance to Malaya quick and unnoticed. Besides, they had the air and naval Supremacy that left the Commonwealth Army on a messy situation. The Japanese killed 145, 703 and 9,800 were left casualties. They further captured 130,000.
During the invasion, the Japanese took advantage of their war experience in China to beat the British. They moved on bicycles with small tanks whereas, the British who depended on the base they had in Singapore got severely disadvantaged.
The thick tropical forests and the terrain took a toll on the British, by the time they were trying to catch up with the Japanese it was too late, the Japanese had taken over the weapons from the civilians in Malaya.