'Clock' (i) was the British final development of Singapore and the southern part of Malaya as the main naval and land base areas for British forces in South-East Asia (late 1930s/early 1940s).

At the time of World War II’s start in September 1939, the naval base in the Johore Strait between Singapore island and the Malayan mainland has been created and was still under development in an intermittent process dating from 1923. In September 1939 the base was protected by emplaced naval weapons including five 15-in (381-mm) guns whose emplacements at Changi (three guns) and Buona Vista (two guns) were still incomplete, five regular infantry battalions (three British, one Indian and one Malay), two volunteer infantry battalions, two heavy coast-defence artillery regiments (with smaller-calibre guns located at Fort Siloso, Fort Canning, and Labrador), three anti-aircraft artillery regiments, four fortress engineer companies, and Royal Air Force squadrons located on Tengah and Sembawang airfields.