What were the efforts made by the British to defend Singapore?

After World War 1, Britain was financially drained and could no longer maintain a strong naval presence in the Far East. Britain needed all its warships to remain in Europe. However, Britain saw the need to defend its empire in the Far East as Japan was building a powerful navy. 

The British Empire in 1939. 

In order to defend its empire in the Far East, Britain decided on the 'Main Fleet to Singapore' strategy. This meant that Britain would send ships from Europe if there was trouble in Asia. However, to maintain the fleet, a huge naval base had to be built in the Far East. Singapore was chosen for the naval base was completed in 1938.

A 50,000 ton dry dock built by the British in the Sembawang Naval Base which was damaged by the Japanese

To defend the naval base in Singapore, 15-inch guns, usually mounted on ships, were installed facing the sea to prevent any attacks from the sea. Military airfields were built in Tengah and Sembawang. Underground bunkers were also built in several places like Fort Canning, Labrador and Sembawang.

The 15-inch guns that was usually mounted on ships. 

It was generally thought that Singapore was protected from the north.

An extract made by the Coordinator of Information in his report published on 12 December 1941: 

The geography of Malaya is a factor in its defence. The coastal plains were about 15 miles in width and filled with mangrove swamps. The mountain range, which runs from north to south is covered with dense jungle and vast areas that are almost unknown. Roads are few and heavily guarded, so that an invading army would be at the mercy of defenders securely hidden in the jungle. 

Singapore was thus known as the 'impregnable' fortress of the British Empire in the East. 

Information taken from : Marshall Cavendish Education (2007). SINGAPORE FROM SETTLEMENT TO NATION PRE-1819 TO 1971. Singapore. MOE Building

Extract adapted from ' Special Memorandum ' , No.16, British Empire Section on 12 December 1941 quoted The Japanese Occupation of Malaya, 1941-1945 by Paul H. Kratoska