Singapore's guns and the ammunition problem

Why did Singapore's coastal guns contribute so little to the land battle?

The expected seaborne threat led to armour-piercing ammunition and unsuitable defensive priorities; more high-explosive ammunition and dual-purpose guns could have been more useful.

The key issue was not merely the direction in which Singapore's coastal guns could fire. The expected seaborne threat led planners to stock armour-piercing ammunition suited to ships rather than enough high explosive for troops and field positions. More high-explosive ammunition and dual-purpose 4.5-inch, 5.25-inch, or other available guns could have contributed to landward defence and air protection. Defending the reservoir required troops as well as better artillery planning, tying the garrison's firepower problems to its wider logistical failure.